A balance experiment was carried out to investigate the effects of betaine monohydrate (BET) or betaine derived from condensed molasses solubles (CMS) as a substitute for methionine and choline on nitrogen (N) balance and total tract nutrient digestibility in weaned piglets. The experiment included four treatments with 32 barrows with an average initial body weight (BW) of 13.5 kg. The supplementation of DL-methionine and choline (positive control = PC) to the basal diet, which was deficient in methionine and low in compatible osmolytes in the form of betaine or its precursor choline (negative control = NC) resulted in a significant increase in N retention of 0.8 g/d. The substitution of DL-methionine and choline with BET or CMS did not affect N retention compared to the PC and the NC treatment either. Feeding the PC diet increased the digestibilities of organic matter, NDF, ADF, NFE, crude ash, Ca, P, methionine, tryptophan and cystine by 1.9%, 7.3%, 9.7%, 1.1%, 6.3%, 13.9%, 7.7%, 15.9%, 4.3% and 2.8%, respectively, and tended (p < 0.20) to increase the digestibilities of most other amino acids by 1.6-3.4%. Digestibility of CP, EE (HCl), Mg and Na was 3.1% (p=0.09), 5.1% (p=0.09), 5.1% (p= 0.06) and 3.3% (p= 0.17) higher, respectively, when compared to the NC treatment. BET and CMS supplementation increased most nutrient digestibilities in the same magnitude as for the PC treatment. In summary, the supplementation of betaine, originating from different sources, to a diet with low contents of compatible osmolytes increased in particular the fermentation of fibre and enhanced mineral absorption. The supplementation of the NC with DL-methionine was more efficient in improving N retention than the replacement of DL-methionine by betaine originating from BET or CMS.