Motor imagery (MI) and action observation (AO) are techniques that have been shown to enhance motor skill learning. While both techniques have been used independently, recent research has demonstrated that combining action observation and motor imagery (AOMI) promotes better outcomes. However, little is known about the most effective way to combine these techniques. This study examined the effects of simultaneous (i.e., observing an action whilst imagining carrying out the action concurrently) and alternate (i.e., observing an action and then doing imagery related to that action consecutively) AOMI combinations on the learning of a dart throwing task. Participants (n = 50) were randomly allocated to one of five training groups: action observation (AO), motor imagery (MI), simultaneous action observation and motor imagery (S-AOMI), alternate action observation and motor imagery (A-AOMI) and a control group. Interventions were conducted three times per week for six weeks and pre- and post-measures of total score were collected. Results revealed that all intervention groups, with the exception of the AO and control groups, significantly improved performance following the intervention. Posthoc analyses showed that S-AOMI group improved to a significantly greater degree than the MI and AO groups, and participants in the A-AOMI group improved to a significantly greater degree than the AO group. Participants in the A-AOMI group did not improve to a significantly greater degree than the S-AOMI group. These findings suggest that combining AOMI, regardless of how it is combined, may be the beneficial method for improving the learning and performance of aiming skills.