FlixBus operates a bus from Paris to Dieppe 3 times a week. Tickets cost $11 - $19 and the journey takes 2 h 25 min. Alternatively, French Railways (SNCF) operates a train from Paris to Dieppe hourly. Tickets cost $14 - $30 and the journey takes 1 h 10 min. French Railways (SNCF) also services this route hourly.
From Paris, Paris La Défense bus to Dieppe. 2 h 25 min 14€. From Paris St Lazare train to Rouen-Rive-Droite then train to Dieppe. 2 h 31 min 33€. From Paris St Lazare RER to Gisors Embranchement, train to Serqueux / Gare SNCF, then bus to Dieppe / Gare SNCF. 4 h 20 min 22€. From Paris drive to Dieppe. 2 h 2 min 25€.