Farrowing crates drastically restrict behavioural opportunities for lactating sows. Temporary crating (TC) systems restrain the sow for the first few days after farrowing and then allow free sow movement in the farrowing pen for the rest of lactation. TC housing systems are promoted because they improve sow welfare in comparison with permanent crating (PC) systems that restrict the sow for the whole lactation. How TC affects piglet welfare is less well understood, as it may be associated with higher mortality by crushing but also with increased positive piglet behaviours. Specifically, it has not yet been investigated whether the free movement of the mother sow, all other things being equal, influences the play behaviour of her piglets. This study compared play behaviour in 10 litters housed in PC pens with 10 litters housed in TC pens shortly after the crate removal (Days 3-6 postpartum, Period 1) and then during the 4th week of lactation (Days 18-27 postpartum, Period 2). The only difference between the two treatments was the free sow movement in TC while all other parameters of the two housing systems (e.g., pen area, floor quality, bedding) were equal. Total play behaviour, piglet-piglet social play and piglet-sow play were substantially more frequent in the TC system in both Period 1 and Period 2. This is the first study to show that giving the sow the freedom of movement within a farrowing pen early in lactation promotes piglet play behaviour. Thus, temporary crating is superior to permanent crating not only in relation to sow welfare but also when it comes to aspects of piglet welfare.