The actor, 44, announced the news in a post on Instagram, alongside a selfie of him and Meyer, 22.
According to The Sun, Galecki wrote: “We are absolutely over the moon to announce that we will soon be welcoming a little one into this crazy and wonderful world.
“We ask that you please respect our privacy during this celebratory time for us and our families. There truly is love out there for all.
View this post on Instagram
We are absolutely over the moon to announce that we will soon be welcoming a little one into this crazy and wonderful world. We ask that you please respect our privacy during this celebratory time for us and our families. There truly is love out there for all. We hope ours is the ember of yours, as we feel yours is the ember of ours.
“We hope ours is the ember of yours, as we feel yours is the ember of ours.”
Galecki stars as socially awkward physicist Leonard Hofstadter in science sitcom The Big Bang Theory, which is coming to an end later this month after 12 years and 279 episodes.
Earlier this week, Galecki — alongside his co-stars Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Mayim Bialik and Melissa Rauch — was immortalised in cement outside Hollywood’s TCL Chinese Theatre.
The actors were the latest stars to place their hand prints outside the Los Angeles landmark.
Galecki and Meyer went public with their relationship in September 2018 and made their red carpet debut together at the E! People’s Choice Awards in November.
Johnny was famously in a relationship for two years with his Big Bang co-star Kaley Cuoco before they split in 2010.
The chemistry from the pair’s on screen relationship transcended the film set. However, the pressure of having a secret romance took its toll and they decided to call it a day.
Cuoco previously said: “It was a wonderful relationship but we never spoke a word about it and never went anywhere together.
“We were so protective of ourselves and the show and didn’t want anything to ruin that. But that also made it sad, too.
“That’s not the kind of relationship I want — I don’t want to be hiding. We couldn’t do anything. It wasn’t as fun as we wanted it to be,” she explained.
Despite the split they remained on good terms, continuing with their hit show which is now in its 12th and final season.
Back in July Johnny even posted a heartwarming comment after Cuoco wed husband Karl Cook.
He wrote: “Couldn’t be happier for my fake wife @normancook and @mrtankcook whose words brought us all to tears last night. So much love for you both.”
This story first appeared in The Sun and is republished with permission.