It was announced last week that spectators, capped at 2,000 per day, would be allowed at the Vivint Houston Open for the first time on US soil since the circuit came out of its Covid-19 lockdown.
While heaping praise on PGA Tour officials for the way it has handled the sport's return to competition, Mickelson is nervous about the step taking place.
"I think that they will do a very good, safe job in having 2,000 people at the Houston Open,'' said the five-time major winner.
"However, for me personally, I don't like the risk that having that happen the week before the Masters.
"I just feel like the week before the Masters, like that's a big tournament we have and I just don't want to have any risk heading in there. So it has made me question whether or not I'll play there.
"But then I have to give the Tour a lot of credit and confidence in the way that they've handled the entire year and I'm sure they're going to do a great job at keeping the players safe in that environment.
"But because I haven't seen it before, because it's the first one out on the Tour with some people, I'm unsure and I don't want to take any unnecessary risks.
"I don't go out to dinner, I don't go out and socialise, because I want to make sure that I have an opportunity to compete in the Masters.''
Next week's Bermuda Championship will be the first PGA Tour event to admit a limited number of spectators since the first round of the Players Championship in March.
On the European Tour, it had been agreed with the Scottish Government that 650 spectators could be in attendance on the Saturday and Sunday of last month's Scottish Open at The Renaissance Club.
But that plan was scrapped on the Friday before the Rolex Series event in East Lothian after Covid-19 restrictions were tightened by First Minister Nicola Sturgeon.
Fifteen positive Covid-19 tests have been reported on the PGA Tour since its restart in June, the latest being former Masters champion Adam Scott.
The Australian withdrew from the Zozo Championship, which starts today in Los Angeles, on the eve of the event, joining world No 1 Dustin Johnson being sidelined at the moment.
Johnson tested positive at last week's CJ Cup at Shadow Creek in Las Vegas.
Mickelson, who is playing in the Zozo Championship, added: I think the PGA Tour's done an incredible job, I mean an incredible job of getting the players to play and compete in a safe environment.
"We've had a few people test positive. It has not spread from those people. They've kept everybody at a good social distance so if somebody does have it, it hasn't affected and carried through the Tour. I think they've done a phenomenal job of having us feel safe.''
If Mickelson decides to skip the Houston event, he is likely to tee up on the Champions Tour in Phoenix instead to complete his Masters preparation.