An end-of-year rally of the type of that money managers like BlackRock's Larry Fink and Dan Loeb have been expecting was possible, but not guaranteed, Tepper reportedly said. Now was the time to tread carefully and not be overextended with stock holdings, he added.
Read MoreDavid Tepper takes short against euro
Tepper's caution Tuesday is reminiscent of the tone he took at another investor conference in May, a time when he was concerned about a multitude of macro issues, including slow growth in the U.S. and a lack of adequate stimulus by the European Central Bank and in China.
In what are now infamous words of warning, Tepper said at the SALT conference in Las Vegas that it was "nervous time" for him in the markets, adding, "I'm not saying go short, but don't be too frickin' long."
Read MoreDavid Tepper on the market: 'I think it's nervous time'
On Tuesday, said the person who attended the Robin Hood speech, Tepper reiterated that the ECB needed to do more to stimulate a struggling European economy, and that the measures that European Central Bank President Mario Draghi had adopted thus far had not been enough to improve matters.
Tepper added that was hoping for more quantitative easing—along the lines of the Federal Reserve's monthly bond-buying program—above and beyond what the ECB announced Tuesday morning, but noted that in the meantime, he is shorting the euro and using put options to predict additional economic pain in France. (He did not elaborate on the details of his French strategy, this person said.)
Tepper could not immediately be reached for comment.