Purpose: This study examines how product packaging influences sales performance among small-scale spice sellers in Mwanza City, Tanzania. It focuses on three packaging dimensions materials, labeling, and design features and assesses their collective and individual effects on sales outcomes. Design/methodology/approach: A descriptive cross-sectional research design was adopted. Primary data were collected from 66 spice sellers in Nyamagana District using structured questionnaires. Quantitative analysis was conducted through SPSS, employing descriptive statistics, correlation, and multiple regression models (Model 1–3) to determine the influence of packaging variables on sales performance. Findings: Results revealed that packaging materials, labeling elements, and design features significantly affect sales performance. Packaging design features had the strongest predictive power (β = 0.628, p < 0.001), followed by labeling elements (β = 0.424, p < 0.01), and packaging materials (β = 0.362, p < 0.05). Collectively, these variables explained over 90% of the variance in sales performance (R² = 0.903). Color emerged as the most influential design attribute, while labeling enhanced credibility through brand and expiry information. Originality/value: This paper extends the application of the Stimulus–Organism–Response (S–O–R) Model and Brand Equity Theory to informal market settings in developing economies, providing empirical evidence from Tanzania’s spice sector a context rarely studied. Practical implications: Findings emphasize the need for small-scale entrepreneurs to invest in cost-effective yet visually appealing and informative packaging. Policymakers and development partners can use these insights to design training and support programs that enhance packaging quality, hygiene, and market competitiveness. Social implications: Improved packaging practices can enhance consumer trust, promote sustainable material usage, and strengthen the livelihoods of micro-entrepreneurs in local food markets.