Against the backdrop of a deepening aging population and the “9073” elderly care framework in China, loneliness has emerged as a serious concern for empty nesters seeking to age in place. Horticultural therapy has increasingly been employed to address this issue. This study focuses on home-based plant companionship, a key aspect of horticultural therapy. Using a questionnaire-based survey, we measured levels of home-based plant companionship, psychological resilience, self-efficacy, and loneliness, and applied structural equation modeling to analyze mediation effects. The results indicate that when the chain mediation variables of “psychological resilience - self-efficacy” are included, the direct effect of home-based plant companionship on reducing loneliness becomes non-significant, while its indirect effect is significant, demonstrating full mediation. Specifically, home-based plant companionship enhances psychological resilience, which subsequently improves self-efficacy, ultimately reducing loneliness. The findings provide new evidence supporting the psychological therapeutic effects of non-human companionship and have practical implications for policy-making, policy-making and the promotion of home-based horticultural therapy as an effective and low-cost approach to improving the psychological well-being of empty nesters.