"If he is the nominee, I will be voting for him, I will be supporting him," Jindal, who also ran for president this cycle, said on CNN. 
The former Louisiana governor argued that under Trump, Republicans have a shot at repealing ObamaCare and putting a conservative justice on the Supreme Court, compared to their prospects with Clinton in the White House.
"I'm not happy about it. I don't think he's the best-qualified candidate. I don't think he's the one most likely to be successful, but I would vote for him over Hillary Clinton," Jindal said.
Jindal was one of the most outspoken critics of Trump before ending his campaign in November, calling Trump "insecure," "weak" and "dangerous" during a speech two months earlier. 
Jindal, who in February endorsed Florida Sen. Marco RubioMarco Antonio RubioRubio: Crisis in Nicaragua could lead to civil war Release of Carter Page surveillance documents reignites debate Graham: Warrant for Carter Page surveillance was 'a bunch of garbage' MORE, predicted on CNN that Trump would not "do a lot of the things that he's said he's going to do."
"I don't think he's a conservative at heart," Jindal remarked. "I don't think he's opposed to big government; I think he just wants to be the one running big government."
Trump led in polls heading into Tuesday's primary in Indiana, where he is hoping to pick up more delegates over chief rival Ted CruzRafael (Ted) Edward CruzDem leaders fend off calls to impeach Trump Cruz: 'I'm glad' Disney fired James Gunn over 'horrible' tweets Washington needs to end hidden inflation tax on our capital gains MORE in his bid to clinch the nomination.