After people found out on Twitter, some users began to protest, using the hashtag #BoycottInNOut.
[Ads /]
One person tweeted, "Tens of thousands of dollars donated to the California Republican Party... it's time to Boycott In N Out - let Trump and his cronies support these creeps... perhaps animal style!"
Another user said, "I've enjoyed the convenience of the drive-thru 3 miles from my house, but no way do they get my money now."
Not all In-N-Out fans are on board with the boycott, though.
One person tweeted, "Sorry I will never #BoycottInNOut I dont care who they donate to."
[Ads /]
Here's a look at some of the tweets from those for and against the boycott:
[Ads /]