Seiji Ozawa, the high-spirited Japanese conductor who took the Western classical music world by storm in the 1960s and ’70s and was music director of the Boston Symphony Orchestra from 1973 to 2002, died on Feb. 6 in Tokyo. He was 88.

The cause was heart failure, said a spokeswoman for the Seiji Ozawa International Academy Switzerland, which announced his death in a news release.

Mr. Ozawa had recently experienced health problems. He never fully rebounded from surgery for esophageal cancer in early 2010, or from back problems that were made worse during his recovery. He was also hospitalized with heart valve disease in later years.

Mr. Ozawa was the most prominent harbinger of a movement that has transformed the classical music world over the last half-century: a tremendous influx of East Asian musicians into the West, which has in turn helped spread the gospel of Western classical music to Korea, Japan and China.

For much of that time, a belief widespread even among knowledgeable critics held that although highly trained Asian musicians could develop consummate technical facility in Western music, they could never achieve a real understanding of its interpretive needs or a deep feeling for its emotional content. The irrepressible Mr. Ozawa surmounted this prejudice by dint of his outsize personality, thoroughgoing musicianship and sheer hard work.

With his mop of black hair, his boyish demeanor and his seemingly boundless energy, Mr. Ozawa captured the popular imagination early on.

He found himself near the top of the American orchestral world in 1973, when he was named music director of the Boston Symphony. He scored many successes over the years, proving especially adept at big, complex works that many others found unwieldy.

He toured widely and recorded extensively with the orchestra. But his 29-year tenure was, many thought, too long for anyone’s good: his own, the orchestra’s or the subscribers’.

Though relatively inexperienced in opera, he left in 2002 to become music director of the august Vienna State Opera, where he stayed until 2010. The rest of his life was mainly consumed with health issues and with dreams of a major comeback on the concert stage, which he was never able to achieve.

Seiji Ozawa was born to Japanese parents in Japanese-occupied Shenyang, China, on Sept. 1, 1935. (The family returned to Japan in 1944.) He studied piano as a child but gave up thoughts of a pianistic career when he broke two fingers playing rugby. He studied conducting under Hideo Saito, the pre-eminent teacher of Western music in Japan, at the Toho School of Music in Tokyo.

In 1959 he traveled to Europe on a cargo ship, bringing a motor scooter and a guitar. He won a competition for orchestral conductors in Besançon, France, that year, and was invited by one of the judges, Charles Munch, then the music director of the Boston Symphony, to study at the Berkshire Music Center at Tanglewood, the orchestra’s summer home in western Massachusetts.

After winning the Koussevitzky Prize for outstanding student conductors there, he returned to Europe. He studied with Herbert von Karajan in Berlin and drew the interest of Leonard Bernstein, who appointed him an assistant conductor of the New York Philharmonic in 1961.

Two years later, not yet well known, he appeared on the television show “What’s My Line?,” on which celebrity panelists had to guess his occupation on the basis of yes-or-no answers. It took them a while. But his ascent had already begun.

In 1964, he became artistic director of the Ravinia Festival in Illinois, the summer home of the Chicago Symphony Orchestra. In 1965, Bernstein recommended him to Walter Homburger, the managing director of the Toronto Symphony Orchestra, who was looking for a music director to replace Walter Susskind. Mr. Ozawa took the job, and his career took off.

He left both those positions in 1969 and was music director of the San Francisco Symphony from 1970 to 1976. From 1970 to 1973, he was also artistic director of the Berkshire Music Center at Tanglewood, sharing the position with the composer Gunther Schuller and solidifying his standing with the Boston Symphony.

Apart from conducting Boston Symphony concerts, Mr. Ozawa’s relationship with Tanglewood over the years was somewhat halting but occasionally eventful. In 1994, the orchestra built a magnificent 1,180-seat auditorium on the campus. Norio Ohga, the president of the Sony Corporation, donated $2 million of the nearly $10 million it cost on the condition that the structure be named Seiji Ozawa Hall.

Storm clouds gathered a few years later, when Mr. Ozawa, after years of relative inactivity at the Tanglewood Music Center, as the school was now called, asserted his prerogatives as the orchestra’s music director.

Complaining of a decline in the quality of the conducting program and insufficient representation of orchestra members on the faculty, he fired a key administrator in 1996. The next year prominent faculty members — including the pianists Leon Fleisher, the center’s artistic director, and Gilbert Kalish, its faculty chairman — left in protest, citing a lack of any clear vision from Mr. Ozawa.

Mr. Ozawa remained active in Japan during his Boston tenure. He became honorary artistic director of the Japan Philharmonic Orchestra (now the New Japan Philharmonic) in 1980. Four years later, he helped found the Saito Kinen Orchestra, a memorial to the beloved mentor of his youth. This spawned the Saito Kinen Festival in Matsumoto in 1992; the event was renamed the Seiji Ozawa Matsumoto Festival in 2015.

Mr. Ozawa finally left the Boston Symphony in 2002. As its music director laureate, he returned to Boston for two concerts at Symphony Hall in 2008.

He last performed at Tanglewood in 2006. He canceled a scheduled return in 2010 for health reasons and had to cancel again in 2016, because he lacked the necessary physical strength on his return to Japan after conducting briefly in Europe.

Mr. Ozawa’s shift to opera came as a surprise, given his limited experience. He made his Metropolitan Opera debut in 1992, conducting Tchaikovsky’s “Eugene Onegin,” and returned only once, in 2008, to conduct Tchaikovsky’s “Queen of Spades.”

At the Vienna State Opera, he was able to fill in many gaps left by a career spent almost entirely in concert halls. But he tended to avoid the standard repertory in favor of the fringes, as in his first big splash: a new production of Ernst Krenek’s jazz-tinged, Weimar-era “Jonny spielt auf” in 2003.

He was also able to conduct and tour with the Vienna Philharmonic, an elite, self-governed contingent of the Vienna State Opera Orchestra. He led the orchestra in three concerts at Carnegie Hall in 2004.

Mr. Ozawa was to make a triumphal return to Carnegie in the 2010-11 season. But the event, though in some ways the culmination of his career, had to be severely curtailed.

In December 2010 he traveled to New York, hoping to conduct the Saito Kinen Orchestra in three programs at Carnegie as part of its citywide festival JapanNYC. But, having suffered through the year with bouts of sciatica, he had to scale back his efforts in each of the first two concerts to a lone major work. He retained just enough of his youthful vigor to finish with a huge effort, conducting Britten’s sprawling, deeply emotional “War Requiem.”

As artistic director of JapanNYC, he was scheduled to return to Carnegie in April 2011 to conduct concerts by the Seiji Ozawa Ongaku-juku, a Japanese youth orchestra. But he had to cancel this and most subsequent engagements.

Mr. Ozawa made a modest international comeback in April 2016, leading the Berlin Philharmonic at the Berliner Philharmonie and the orchestra of the Seiji Ozawa International Academy Switzerland in Paris.

Complete information on survivors was not immediately available.

In the waning years of his life, Mr. Ozawa came to recognize the wisdom that comes from years of music making.

“A musician’s special flavor comes out with age,” he said in “Absolutely on Music,” a 2016 book of conversations between Mr. Ozawa and the novelist Haruki Murakami. “His playing at that stage may have more interesting qualities than at the height of his career.”