The Kings of Leon frontman's wife - model Lily Aldridge - is three months pregnant, according to E! Online.
The couple confirmed to People through a representative: "We are thrilled to announce that we are expecting our first child together. We can't wait to meet the new addition to our family."
His cousin Matthew, who is the band's lead guitarist, welcomed first son Knox Cameron Patrick Followill with wife Johanna Bennett in April.
Followill and Aldridge married at a small ceremony in California in mid-May, with Aldridge quoted as saying that the occasion was "more beautiful than I could've imagined".
Kings of Leon cancelled a string of US tour dates this summer on account of Followill's "vocal issues and exhaustion", resuming their tour as planned in Canada in late September.
Followill's bandmates were then forced to deny reports that he had been dismissed from the band over his behaviour.
Kings of Leon were recently nominated for two Grammy Awards.
Watch Jared and Matthew Followill of Kings of Leon discuss their Grammy-nominated documentary Taliniha Sky with Digital Spy below: