Term for self-serving behavior disguised as altruism? [duplicate]

Solution 1:

I am not sure if you are stuck to the notion of altruism, but in the context of making a show of being nice to others to make themselves feel good, you could use sanctimonious.

Sanctimonious is a twist on the words sanctity and sacred, which mean holy or religious. A sanctimonious person might think he's holy, but their attitude comes across more like "holier-than-thou." Though sanctimonious people might try to act like saints, their actions are far from pure or holy, which just makes them sound like hypocrites.
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Solution 2:

As defined by Merriam-Webster, egoism (or egotism) is "a doctrine that individual self-interest is the actual motive of all conscious action." A person who exhibits this egoism is an egoist (or egotist). These terms are discussed extensively in another Stack Exchange entry.

What you have described is egoism disguised as altruism--or, as both talmu and Doug Warren have mentioned, false altruism. Further examples of egoism or false altruism can be found on this Quora post. Some of them, taken from the answerer's own experiences, include

"donating to a charity to attend a benefit, peer tutoring in 10th grade chemistry because there were a lot of cute girls in the class, [and] giving away items when graduating college because I was too lazy to move them to the dumpster."

Solution 3:

Hypocritical comes to mind.

The noun form of the adjective is

hypocrisy n
1. The practice of professing beliefs, feelings, or virtues that one does not hold or possess; falseness.

TFD