January – February – March – April – May – June – July – August – September – October – November – December
- April 2, 1900 - The Foraker Act is signed into law, establishing a civilian yet democratically-limited government.
- April 3, 2005 - Death of Tony Croatto, Italian-Puerto Rican singer and composer (b. 1940 or 1939)
- April 5, 1944 - Birth of Pedro Rosselló, sixth Governor of Puerto Rico
- April 6, 1897 - Birth of Jesús T. Piñero, first native Governor of Puerto Rico (d. 1952)
- April 7, 1838 - The Municipality of Ceiba is founded.
- April 7, 2004 - Death of Victor Argo, actor (b. 1934)
- April 8, 1827 - Birth of Ramón Emeterio Betances, main leader of the Grito de Lares and father of the Puerto Rican independence movement. (d. 1898)
- April 10, 1874 - The Municipality of Maricao is founded.
- April 12, 1848 - Birth of José Gautier Benítez, famous poet (d. 1880)
- April 12, 1929 - Birth of Luis Vigoreaux, radio and television show host, announcer, comedian and producer (d. 1983)
- April 12, 1935 - Birth of Baltasar Corrada del Río, former Resident Commissioner of Puerto Rico
- April 12, 1944 - Birth of Federico Hernández Denton, Chief Justice of the Supreme Court of Puerto Rico
- April 12, 1958 - The first Puerto Rican Day Parade is held in New York City
- April 12, 1968 - Plaza Las Américas opened to the public
- April 12, 1975 - Death of Tomás Blanco, writer and historian (b. 1897)
- April 13, 1967 - Birth of Olga Tañón, two-time Grammy Award and three-time Latin Grammy-winning Merengue & Latin Pop artist
- April 15, 1868 - Birth of Antonio R. Barceló, politician and father of Governor Carlos Romero Barceló (d. 1938)
- April 16, 1866 - Birth of José de Diego, statesman, journalist, poet and advocate for Puerto Rico's independence from Spain (d. 1918)
- April 17, 1921 - Birth of Graciela Rivera, singer
- April 18, 1873 - Birth of Ana Roque, one of the founders of the University of Puerto Rico (d. 1933)
- April 21, 1927 - Birth of José Miguel Agrelot, Puerto Rican comedian, radio and television host and media icon known for his Don Cholito character (d. 2004)
- April 24, 1898 - Birth of Ernesto Ramos Antonini, co-founder of the Partido Popular Democrático de Puerto Rico (Popular Democratic Party of Puerto Rico) (d. 1963)
- April 24, 1977 - Birth of Carlos Beltrán, Mayor League Baseball outfielder
- April 26, 1827 - The Municipality of Lares is founded.
- April 26, 1933 - Birth of Filiberto Ojeda Ríos (d. 2005)
- April 28, 1950 - Birth of Willie Colón, salsa musician