The aim of this study was to compare the effects of different housing systems on behaviour and growth performance of fattening pigs. Forty Duroc × Meishan pigs aged 100 d were assigned into two housing systems: indoor deep litter (DL) housing (4 pens with 5 pigs/pen) and indoor pen with outdoor playground (PG; 4 pens with 5 pigs/pen). Pig behaviour, body weight, and feed intake were recorded and analysed. Results showed that DL pigs spent more time exploring (DL: 231.0 vs. PG: 178.0 s/h, P < .01), while PG pigs were more aggressive (PG: 6.6 vs. DL: 0.4 s/h, P < .01) and engaged in higher levels of abnormal behaviour (PG: 20.0 vs. DL: 3.2 s/h, P < .01), specifically stereotyped behaviour and mouth-holding/biting tail. No difference was observed for the final body weight and feed conversion efficiency. The results of this study suggest that the DL system improves pig welfare at aspects of exploratory behaviour and abnormal behaviour compared with the PG housing system under the conditions studied, providing a basis for the selection and design of optimum housing systems for pigs.