The couple started dating in March 2016 after Cuoco had ended her 21-month marriage to tennis player Ryan Sweeting.
"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," Galecki said on Instagram alongside a black and white photo of himself holding hands with Cuoco who is seen wearing a lace wedding gown.
Galecki's caption is a reference to how his "The Big Bang Theory" character Leonard is married to Cuoco's Penny on the long-running sitcom.
The pair had also dated in secret from 2008 to 2010.
"Deepest congrats to the newlyweds. Love you both so much @normancook & @mrtankcook So moved by tonight," Galecki said in a second shared image from the wedding that also featured the couple.
"Yes we are thrilled to be at @normancook and @mrtankcook 's gorgeous wedding and it's super fun. Right @itswilwheaton!?" Bialik said alongside a collage of photos take from the wedding including looks at the food served and fellow guest Wil Wheaton.
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Television personality Brad Goreski, who was also present at the wedding, posted on Instagram a video of Cuoco walking down the aisle to meet Cook.
"Last night was magical! Congratulations @normancook & @mrtankcook! Love you guys so much! Wishing you many years of happiness! #kcsquared," he said.
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