Casein-based films have excellent gas-barrier properties and strength appropriate to form a variety of edible food packaging, but do not constitute strong moisture barriers. In prior work, we used humidity-controlled DMA (DMA-RH) to show that solvent-cast films from calcium caseinate (CaCas, 75% dry basis) and glycerol plasticizer (Gly, 25% dry basis) of 0.03–0.05 mm thickness are extremely sensitive to ambient relative humidity (RH) and temperature (T) and melt around Tm~45°C at 50% RH, or RHm~67% at 20°C; Tm also decreases at higher RH, which limits the usefulness of CaCas packaging films in warm and/or humid conditions. Citric pectin (CP, 0.1 to 2% dry basis) was explored as an edible additive to crosslink CaCas/Gly films with the objective to improve their environmental resistance. CP was added to water/Gly solutions, stirred for 1h, then CaCas was added and stirred for 1 h. Dynamic T-ramps (10–70°C) with an AR2000 rheometer showed that at 25°C, CP% strongly increased the viscosity and storage modulus, G′, of the solutions near-exponentially, signifying strong binding of CP with CaCas; in addition, new crosslinks were activated between ~42–60°C for 1–2% CP. DMA-RH (Q800) T-ramps of dried films at 50% RH showed that 0.1–0.5% CP softened the films and reduced G′ due to steric hindrance of isolated CP particles throughout the CaCas network, while 1 to 2% CP increased G′, demonstrating a higher crosslink-density in the films. Tm increased to ~50°C with 1% CP and ~60°C with 2% CP. Optical microscopy imaging confirmed strong changes in the CaCas/Gly/CP network as a function of CP content. Moisture sorption RH-ramps at 20°C (Q5000SA) indicated that CaCas films absorb ~10% of their weight in water at 50% RH and up to ~28% at 80%RH; adding up to 2% CP reduced water-sorption by up to 15% at high RH. High CP% (0.75–2%) slowed dissolution kinetics of the films in water at 20°C, while low CP% (0.1–0.5%) accelerated solubilization slightly. CaCas films strengthened with > 1–2% CP are more environmentally-resistant and have the potential to replace or improve some synthetic food packaging to reduce waste and/or add functionality and nutrition to food products.