Descartes sought certainty because he thought that if we know something with certainty, then it must be true. And he was right, if only because 'S knows that p' implies p, so that in 'We know with certainty that . . .' the phrase "with certainty" is redundant; there is no such thing as uncertain knowledge. I suspect that the sense of your question may be Cartesian: is it the case that certainty implies truth? There are several concepts to sort out here: 'We know for sure, or for certain, or with certainty that . . .', 'I am certain (sure) that . . .', 'I feel certain, sure, that . . .', 'It is certain that . . .' (but not 'It is sure that . . .') There is a very useful paper by G.E. Moore called "Certainty" that might be helpful here, which is sensitive to distinctions of this kind. Sean is right in his response above that psychological certainty or "feeling certain" may not be a mark of truth, though I wonder whether anyone has troubled to test the correlation empirically in humans, and whether it makes sense to think about testing it in animals. On the other hand it also seems correct that if something is indeed certain, e.g. that 7×9 = 63, then '7×9 = 63' is true.
Does certainty suggest or indicate truth?