The former Sister Sister star is expecting her first child with her husband Adam Housley, People reports.
"Adam and I are excited about having a baby and the blessing that he or she will bring to our lives and to our family and friends," Tamera said.
"We can't wait to meet this little miracle!"
Tamera had said in October that she was not planning on having children "anytime soon", but has now revealed that she changed her mind after a trip to South Africa.
"Adam and I looked at each other and said, 'Why not?'" she explained.
Tamera's twin sister Tia Mowry had her first child, a son called Cree Taylor, last June.
The siblings appear in the Style reality show Tia & Tamera, which was renewed for a second season last September.
> Tamera Mowry: 'It was difficult to give up space after marriage'