An adapter block assembly includes two housing pieces that cooperate to hold one or more adapters therebetween. The two housing pieces are removably latched together. Labels can be placed over the latches. Certain types of adapter block assemblies are configured to receive multi-fiber plug connectors. Certain types of adapter block assemblies include securement arrangements at opposite ends thereof to aid in mounting the adapter block assemblies to frames, trays, chassis, or other such structures.