This paper presents a decentralized model reference adaptive control (DMRAC) for interconnected subsystems with unknown and/or time-varying time delay. The decentralization approach is based on the interconnection output estimation using the polynomial series which offers a general solution for interconnected subsystems. The parameter estimation scheme is a combined adaptive data filtering with a recursive least-squares algorithm with parameter projection and signal normalization. A "good data" model is defined by an adaptive filtering of the input and output signals. The obtained model permits to deal with non-minimum phased subsystems with unknown or time-varying dead time and at the same time to relax the hypothesis of weak interconnections for decentralized control. The performance of the studied scheme is illustrated by numerical examples.