"As the Dow continues to make new highs, yet the Russell, the Nasdaq seem to be showing signs of weakness, it is a little disconcerting to me," said Gartman on CNBC's "Fast Money."
He explained that the divergence reminds him of the bifurcated market of the early 1970s when the "Nifty Fifty" and the Dow kept pushing to new highs while the broad market was faltering.
Gartman added that it was still a bull market, and therefore, "the most bearish one can be here, is neutral."
In Monday's issue of "The Gartman Letter," Gartman wrote, "With each passing day, we are more and more fearful too that a correction of some very real magnitude is hard upon us as the broader market indices such as the Russell and the NASDAQ have now 'failed' well below their previous highs and as upward sloping trend lines cast back into last year have been broken through to the downside."
—By CNBC's Leanne Miller.