Both series - which have been struggling in the ratings - have been aired twice weekly since January 6, but will now revert to screening on just Tuesday nights, Deadline reports.
However, axed horror drama 666 Park Avenue - which previously aired on Sunday nights - will not return to its former slot. Instead, ABC plans to air repeats of popular comedy Modern Family.
The twice-weekly airings of Apartment 23 and Happy Endings saw both shows plunge to new series ratings lows. On January 13, Happy Endings pulled in 2.07m viewers and Apartment 23 attracted just 1.73m.
The two series will now continue to air on Tuesday nights between 9pm and 10pm. ABC president Paul Lee recently insisted that no decision has been made on the future of either show, despite the falling audience numbers.
In the UK, both Happy Endings and Don't Trust the B---- in Apartment 23 are broadcast on E4.
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Watch a clip from Happy Endings below: