The parish church of Portovenere, dedicated to San Lorenzo, stands in a small square just inside the medieval gate at the northern end of the village. It is a Romanesque building from the 12th century, with a striped marble facade that echoes San Pietro's but is more restrained — a wide arched portal flanked by carved columns, the surface in the same black-and-white banding that signals Genoese patronage.
Inside, the main object of interest is the Palmarino altarpiece: a painted panel depicting the Virgin of the Assumption, sheltered beneath a stone baldachin in the left aisle. The altarpiece is said to have washed ashore on Palmaria island and was brought to the church on the orders of the Genoese lord. The church also holds a painted processional cross of the 13th century and a marble font carved with scenes of the Baptism.