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We study dynamics of entropy perturbations in the two-field assisted darkenergy model. Based on the scenario of assisted dark energy, in which onescalar field is subdominant compared with the other in the early epoch, we showthat the entropy perturbations in this two-field system tend to be constant onlarge scales in the early epoch and hence survive until the present era for ageneric evolution of both fields during the radiation and matter eras. Thisbehaviour of the entropy perturbations is preserved even when the fields arecoupled via kinetic interaction. Since, for assisted dark energy, thesubdominant field in the early epoch becomes dominant at late time, the entropyperturbations can significantly influence the dynamics of density perturbationsin the universe. Assuming correlations between the entropy and curvatureperturbations, the entropy perturbations can enhance the integrated Sachs-Wolfe(ISW) effect if the signs of the contributions from entropy perturbations andcurvature perturbations are opposite after the matter era, otherwise the ISWcontribution is suppressed. For canonical scalar field the effect of entropyperturbations on ISW effect is small because the initial value of the entropyperturbations estimated during inflation cannot be sufficiently large. However,in the case of k-essence, the initial value of the entropy perturbations can belarge enough to affect the ISW effect to leave a significant imprint on the CMBpower spectrum.

Dynamics of entropy perturbations in assisted dark energy with mixed kinetic terms