Combustor dome assemblies having combustor deflectors are provided. For example, a combustor dome assembly comprises a combustor dome defining an opening; a ceramic matrix composite (CMC) deflector positioned adjacent the combustor dome on an aft side of the assembly; a fuel-air mixer defining a groove about an outer perimeter thereof; and a seal plate including a key. The CMC deflector includes a cup extending forward through the opening in the combustor dome that defines one or more bayonets and a slot. The bayonets are received in the fuel-air mixer groove, and the seal plate key is received in the CMC deflector slot. In another embodiment, where the seal plate may be omitted, a spring is positioned between the fuel-air mixer and the CMC deflector to hold the CMC deflector in place with respect to the combustor dome. Methods of assembling combustor dome assemblies having CMC deflectors also are provided.