Background: Household waste management in Indonesia remains difficult to translate from environmental awareness into sustained household practice. Kampung Ramah Lingkungan (KRL) program combines community participation with local institutional support. Purpose: This study examines how environmental communication and multi-stakeholder collaboration are associated with household waste management intention and behavior in KRL communities. Methods: A quantitative survey was conducted with 386 adult residents across eight purposively selected KRL sites. Seven constructs were analyzed using partial least squares structural equation modeling (PLS-SEM) in SmartPLS 4. Results: Multi-stakeholder collaboration showed the strongest direct association with intention (β = 0.766, p < 0.001) and the largest total association with behavior (β = 0.515, p < 0.001). Environmental communication was not directly associated with intention (β = −0.018, p = 0.756), but it was positively associated with perceived behavioral control, attitude, and subjective norm. Its total association with behavior was positive (β = 0.110, p = 0.002), including an indirect pathway through perceived behavioral control (β = 0.096, p = 0.001). Intention was positively associated with behavior (β = 0.426, p < 0.001). Conclusion: KRL waste management is better explained by the interaction of behavioral dispositions with communication and collaborative conditions than by individual predispositions alone. Implications: Communication strategies should combine practical guidance and meaning-making with coordination, accessible facilities, and sustained community support.