Rachel McAdams Brings Son On Family Stroll Five Months After Secret Birth

We're getting our first look at Rachel McAdams as a new mom ... and she fits the part!!!

Rachel and baby daddy Jamie Linden took a family stroll Wednesday in Los Angeles, giving everyone their first glimpse at the couple's 5-month-old son. Rachel kept her pregnancy on the down low and secretly gave birth in April.

The suspense was killing us, but the wait was totally worth it ... just look at that happy fam!!!

Rachel seems to have this mommy thing down pat ... and Jamie looks extremely pleased to be pushing a stroller -- wouldn't you if "The Notebook" star was your baby mama?!?!