This study was conducted to investigate the effects of different levels of fermented oat meal on growth performance, diarrhea incidence, fecal microorganisms, and emission gas in weaned pigs. A total of 80 crossbred piglets (7.31 ± 0.24 kg) weaned at 21 days of age were assigned to treatments in a randomized complete block design based on the initial body weight (BW). This experiment included 2 phases. In the first phase (from 0 to 21 d), there were 5 treatments: T1 (15% nature oat), T2 (3.7% fermented oat + 11.3% nature oat), T3 (7.5% fermented oat + 7.5% nature oat), T4 (11.3% fermented oat + 3.7% nature oat), T5 (15% fermented oat). In the second phase (from 21 to 35 d): T1 (7% nature oat), T2 (1.75% fermented oat + 5.25% nature oat), T3 (3.5% fermented oat + 3.5% nature oat), T4 (5.25% fermented oat + 1.75% nature oat), T5 (7% fermented oat). Pigs had access to feed and water ad libitum and their BW and average daily feed intake (ADFI) were measured for each phase throughout the duration of the experiment. During the first phase,the use of 7.5%, 11.3% and 15% fermented oat to replace nature oat improvedaverage daily gain (ADG) and gain/feed ratio (G/F) (P<0.05). . During the second phase, the use of 3.5%, 5.3%, and 7% fermented oat to substitute nature increased ADG. Entire period of this experiment, T3 and T4 treatments were presented higher ADG, G/F compared with T1 and T2 treatments. Different levels of fermented oat didnot affect diarrhea incidence score, digestibility, fecal microorganisms and emission gas. It is concluded thatfermented oat can serve as an alternative feed ingredient for possibly replacing the use of nature oat.