In Lynnfield, Route 129 leaves Route 1 at the Lynnfield Tunnel, a traffic landmark just south of I-95 and Route 128. Just east of this point, Route 129 enters Goodwin Circle, which provides access to all three highways via a connector road. Immediately after leaving the circle, Route 129 enters the city of Lynn. In Lynn the route heads southeastward, above the Lynn Woods Reservation, twisting around Sluice Pond before meeting Route 129A next to Flax Pond. At this intersection, Route 129 turns southwest along Boston Street before turning southeast on Washington Street, where it crosses Route 107. After passing east of Lynn Common, the route splits, with the eastbound side staying on Washington Street and the westbound following Central Avenue and Exchange Street. Both directions meet again on Route 1A, staying concurrent with that route until meeting the eastern end of Route 129A, turning south before turning eastward once more an entering Swampscott.