<p>The aim of this paper is to study the impact of agglomeration forces and dispersion related to the industrial structure and regional economic size on regional economic growth, as measured by total factor productivity. We use spatial econometric techniques for panel data to explicitly account for spatial effects (proximity interaction and spatial heterogeneity) as well as individual and temporal effects. The estimation results are derived from a sample of 2086 manufacturing firms operating in 138 delegations across the Tunisian coast, observed over the period from 2000 to 2012. Our results show that regional growth is influenced by agglomeration economies. Furthermore, we have identified the existence of spatial economic interactions among the various delegations of the Tunisian coastal area. Diversity, competition, and research and development expenditure have both direct and indirect positive effects on total factor productivity, while specialization appears to have no spatial spillover effect. Our results confirm the existence of significant spatial heterogeneity in the impact of agglomeration economies on total factor productivity. This heterogeneity is particularly evident through the differentiated effects observed across the three identified clusters. Our results advocate for a shift toward development strategies that are spatially differentiated and sensitive to regional contexts.</p>