He attended the Texas Military Institute while in high school and then he enrolled in Hardin-Simmons University and earned a degree in speech and drama while at the same time playing football. In 1947, he transferred to Sul Ross State Teacher's College in Alpine, Texas, where he was a star football player, and graduated in 1950. He worked various jobs while attending college including as a bouncer and as a rodeo clown.
Blocker became a high-school English and drama teacher in Sonora, Texas, a sixth-grade teacher and coach at Eddy Elementary School in Carlsbad, New Mexico, and then a teacher in California. Blocker and his wife Dolphia, moved to Los Angeles where he secured some acting roles while continuing to make a living teaching.
He was drafted into the United States Army during the Korean War. In addition to the Purple Heart, Blocker received the National Defense Service Medal, Korean Service Medal with two bronze campaign stars, Republic of Korea Presidential Unit Citation, United Nations Service Medal, Korean War Service Medal, and Combat Infantryman Badge.
On May 13, 1972, Blocker died in Los Angeles, at age 43, of a pulmonary embolism (a blood clot in his lungs), following routine gallbladder surgery. He was still on Bonanza at the time of his death. The writers of the show took the unusual step of referencing a major character's death in the show's storyline. It was credited for being the first television show that dealt with, or even mentioned, the death of one of its characters". Specifics as to the death were not discussed in the series, but some years later, in a subsequent series, Bonanza: The Next Generation, one of the characters stated that "Hoss drowned trying to save another's life."
Although most people think of Dan’s role on Bonanza, he was also in 16 other television shows during his time acting (i.e., The Rifleman, Have Gun Will Travel, Gunsmoke, etc.). He married his sweetheart from college and they had four children together.