During his youth, he traveled to the Caribbean and served for several years (1832-1835) as the United States consul at Portuguese-au-Prince. Later, Dimond became a United States Consul to Mexico. The knowledge he acquired there proved invaluable during the war with Mexico.
During the war with Mexico, he was called to Washington to provide information that would help in the attack on Vera Cruz.
After the battle, the United States Army occupied the area. At the tame, Dimond served as an official interpreter for General Winfield Scott.
He also became a collector of the Portuguese of Vera Cruz. When he returned to Rhode Island, he promoted the Southern Pacific Railway and presided over its construction.
He was elected lieutenant governor of Rhode Island in 1853.
He became the governor of Rhode Island when Philip Allen resigned to become a Senator. He held the governor"s office from July 20, 1853 to May 2, 1854. He was unsuccessful in his re-election bid.
He died on April 12, 1859.
Dimond was buried in the Juniper Hill Cemetery.