"My guys," Robertson wrote on Sunday alongside a photo of Preciado relaxing on a hospital bed as their newborn son rested nearby. "So in love over here. Happy Father's Day."
The new mom also shared pics and videos of herself with her baby boy, and documented their journey heading home from the hospital.
Robertson vied for Ben Flajnik's heart on season 16 of The Bachelor in 2012. She accepted Flajnik's proposal in the season finale, but they broke up in October 2012. Robertson also dated Arie Luynedyk Jr. before getting together with Preciado.