Recently, the decision feedback channel estimation based on the minimum mean square error criterion (DF-MMSE-CE) using a fixed DF filter coefficient has been proposed to improve the channel estimation accuracy for DS-CDMA with frequency-domain equalization (FDE). In this paper, we propose adaptive DF (ADF)-MMSE-CE, in which the DF filter coefficient is adapted to changing channel conditions based on a recursive least square (RLS) algorithm. Furthermore, the channel estimate is phase corrected upon the reception of the periodically inserted pilot chip blocks. The average BER performance of DS-CDMA with MMSE-FDE using ADF-MMSE-CE is evaluated by computer simulation in a frequency-selective Rayleigh fading channel and the simulation results show that our proposed scheme is very robust against fast fading.