We studied effects of two weaning procedures on the development of pigs raised in a multi-suckling (MS) system with five sows and their litters. One MS group was subjected to a gradual weaning treatment during a lactation period of 9 wk, which included forced intermittent-suckling (IS) for 10 h/d during the fifth wk of lactation, followed by a 4-wk period in which sows could voluntarily get away from their piglets (IS9 treatment). The other MS group was weaned abruptly at 4 wk of age and was subsequently housed in a nursery (A4 treatment). At 9 wk of age, pigs from both treatments were relocated to a finishing unit, where they were housed in a group of max. 35 pigs per treatment. Five consecutive batches of 10 sows and their litters were studied. Weaning had a more profound impact for the A4 pigs than IS and sow-initiated separation did for the IS9 pigs, demonstrated by a lower weight gain between d 27–33 (0.90 ± 0.08 vs. 1.51 ± 0.06 kg/pig, F1,4 = 25.23, p < 0.01), indications of a higher diarrhea occurrence, a distinct peak in belly-nosing behavior and numerically higher levels of aggression and damaging oral manipulation between wk 4–9. For IS9 pigs, weaning seemed to have less impact; feed intake after transition to the finishing unit was similar in both treatments, indicating that IS9 pigs had a more successful transition to a diet of only solid feed, and IS9 pigs showed no growth check, nor behavioral indicators of having difficulty coping with the post-weaning situation. The extended weaning process likely gradually prepared the gastro-intestinal tract to process solid feed, which may explain the better performance of the IS9 pigs. Additionally, benefits of the gradual weaning treatment were reflected in behavioral differences over the entire experiment; between 4–18 wk of age, IS9 pigs overall showed less belly-nosing, less damaging oral manipulation and had fewer lesions related with manipulation and aggression than A4 pigs. This may altogether indicate a less stressed state of the IS9 pigs. To conclude, IS9 pigs coped better with both transitions than A4 pigs did and the gradual weaning treatment had long-term beneficial effects, particularly concerning behavior. Therefore, gradual weaning in a multi-suckling system seems promising for improving piglet performance, behavior and welfare.