To examine whether alternating training with both the non-paretic and paretic sides (alternating bilateral training), expecting trial-to-trial inter-limb transfer of training effects from the nonparetic to the paretic side, improves upper-limb motor performance in post-stroke patients, compared with unilateral training involving only the paretic side. An assessor-blinded pilot randomized controlled trial. Twenty-four right-handed post-stroke patients with hemiparesis. Participants were randomly allocated to either an alternating bilateral training group or a unilateral training group (n = 12/group). Participants underwent dexterity training of the paretic arm using the Nine-Hole Peg Test, completing 10 trials/day for 7 consecutive days. The alternating bilateral training group additionally performed alternating trials with the non-paretic limb. Performance change, assessed 1 day and 1 week after the 7-day training period, was compared between groups. Although the improvement was comparable in both groups at both post-training time-points, a sub-analysis in which those with left hemiparesis and those with right hemiparesis were analyzed separately revealed potential benefits of the alternating bilateral training, specifically for those with left hemiparesis. Alternating bilateral training may augment training effects and improve upper-limb motor function in patients with left hemiparesis.