His fame in Sweden began in 1970, working alongside Lasse Hallström and Brasse Brännström on a television show named "Oj är det redan fredag" (Oh, is it already Friday?). His working relationship with Brasse Brännström continued over the years with appearances in cabaret, theatre and television shows. In 1973-74, the pair created a television children's program titled "Fem myror är fler än fyra elefanter" (Five ants are more than four elephants) together with Eva Remaeus. Härenstam was the host of the Swedish version of "Jeopardy" between 1991 and 2005. In 2015, he published his autobiography "Morsning & Goodbye".