Abstract: All-foam mattress assemblies with foam engineered cores having thermoplastic and thermoset materials, and related assemblies and methods are disclosed. All-foam mattress assemblies use foam-based materials, such as thermoplastic and thermoset, to provide cushioning and support characteristics for a user in the sleeping area of a mattress during sleep or rest. The all-foam mattress assemblies may include foam comfort layer(s), foam transitional layer(s), and a foam engineered core. The all-foam engineered core may lessen a density of a mattress assembly by comprising thermoset member(s), and engineered geometric thermoplastic material profile(s) adjacent to the thermoset member(s). The engineered geometric thermoplastic material profile(s) may be disposed in a parallel or substantially parallel arrangement.