The invention relates to a method for assembling a fluid product dispensing device comprising the following steps: pre assembling a first unit comprising a body (10) and a lateral actuation system (40) including a supporting element (42) mounted on the body (10) such that it can pivot about an axis (A) an actuation element (41) being mounted on the supporting element (42) such that it can pivot about an axis (B) said supporting element (42) comprising a pre assembled position in which the lateral actuation system (40) is blocked assembling a second unit comprising a dispensing member (30) such as a pump or valve mounted on a container (20) by means of a mounting ring (60) in the first pre assembled unit and moving the supporting element (42) from the pre assembled position to a final assembled position which is axially offset in relation to the pre assembled position and in which the actuation element (41) co operates functionally with the mounting ring (60) in order to actuate the dispensing member (30) each time the lateral actuation system is actuated.
