He was a National Master strength player during his peak years, and was Philippine national champion on two occasions (1956, 1960). He represented his country at five Chess Olympiads: Moscow 1956, Munich 1958, Leipzig 1960, Varna 1962, and Havana 1966. He met some distinguished opposition as a result, losing games against Pal Benko and Ludek Pachman at Moscow 1956, Oscar Panno at Munich 1958, Mikhail Tal and Miguel Najdorf at Leipzig 1960, and Lev Polugaevsky at Havana 1966.

He became involved in FIDE as a national delegate, and worked his way into prominence in Asian chess organization. Campomanes often boasted that he was close to the former Philippine President Ferdinand Marcos. Campomanes helped to organize the World Championship match at Baguio, Philippines, in 1978, between Anatoly Karpov and Viktor Korchnoi.

He is best remembered as the President of the international chess organization FIDE. He was elected to that post in 1982, and held it until 1995, through several controversies, most notably the abandonment of the 1984–85 World Championship between Anatoly Karpov and Garry Kasparov without result, after 48 games, and the break-away from FIDE of the Professional Chess Association in 1993. The cancellation threw the international chess calendar into disarray for the next several years, since a series of matches had to be held to resolve the matter, and these affected other qualifying events.A soon to be released book claims Campomanes was a KGB agent: "The KGB plays chess" (Boris Gulko, Viktor Korchnoi, Vladimir Popow and Juri Felschtinski): "FIDE President Campomanes, who was already a KGB agent, was persuaded with the help of numerous promises and presents to prevent Karpov's defeat at any expense. At the same time [USSR Chess Federation President, Vitaly] Sevastianov turned to Campomanes. With the signature of [deputy chairman of the KGB] Bobkov a proposal was finally sent to the Central Committee of the Communist Party of the Soviet Union to terminate the match and start again with a 0-0 score. The intention was to avoid the impression that the decision favoured Karpov. But mainly people did not want to displease Kasparov's powerful patron Gaidar Alijev. The Central Committee supported the proposal of the KGB and Campomanes terminated the match." More commonly known is the quote following the press conference which terminated the match, overhead by ESPN cameras, reported in Chess Life by witness Max Dlugy and Sports Illustrated: "But Anatoly, I told them just what you said".

On the positive side, the membership of FIDE grew significantly, by about 50 member nations, during his tenure as FIDE president. Campomanes was succeeded as FIDE President in 1995 by Kirsan Ilyumzhinov. He was appointed as FIDE Honorary President, and was often present at significant international competitions such as zonal and continental championships, chess olympiads, and world chess championships

Campomanes was the only Filipino to ever hold the highest position at FIDE, the world chess governing body based in Lausanne, Switzerland.

On 5 February 2003, the Philippine anti-graft court Sandiganbayan convicted Florencio Campomanes, the former FIDE president, for failure to account for the Philippine Sports Commission (PSC) government funds amounting to PhP12.876 million (or US$238,746 at an exchange rate of PhP53.932 = $1). The PSC entrusted these funds to the FIDE for the World Chess Olympiad in Manila, hosted by the Philippine government from 6 to 25 June 1992. Subsequently, Florencio Campomanes was sentenced to one year and 10 months imprisonment. According to a FIDE Press Release, dated 16 January 2007, Campomanes was cleared of these charges by the Philippine Supreme Court in December 2006, though FIDE's release states that the penalty was the equivalent of a 100 euro fine.

The charges against Campomanes' were overturned based upon a technicality. There was never any resolution about what happened to the 12.876 million pesos mentioned in the above paragraph. The rationale for the overturn was that the Supreme Court of the Philippines decided that Campomanes was not a government official to whom the anti-graft laws applied. Thus as a non-government official, Campomanes had no duty under the law he was prosecuted to render an accounting of the 12.876 million pesos.

In early February 2007, Florencio Campomanes suffered injuries from a car accident, at which time he was in intensive care.

On 3 May 2010, Campomanes died in the Philippines.

Moscow 1956–Board 2, Munich 1958–Board 3, Leipzig 1960–Board 1, Tel Aviv 1964–Board 4, Havana 1966–Board 4;