Dissipative trapped particle modes are studied in tandem mirrors by including electron collisions and ion Landau damping. A variational approach is used to obtain a collisional response in terms of the collisionless result plus a collisional term. The collisional term is then self‐consistently solved in all collision frequency regimes. When &ngr;/&ohgr;≪1 (&ngr;≡electron collision frequency) and the dissipationless mode is stable through a positive (negative) charge uncovering mechanism, there are two stable waves with phase velocities in the ion (electron) diamagnetic direction. The higher frequency wave with &ohgr;∼&ohgr;@B|i(&ohgr;*e) is destabilized by ion (electron) dissipation while the lower frequency wave is destabilized by electron (ion) dissipation. At high collision frequency (&ngr;>&ohgr;@B|e), the only unstable trapped particle wave has &ohgr;∼&ohgr;*e, with electron collisions being destabilizing.