This study investigates the effect of trade openness and financial openness on output growth volatility in Nigeria using annual time series data that span the period from 1970 to 2015. Output growth volatility is generated using an EGARCH (1,1) process, and this was regressed on indices or measures of trade openness, financial openness (using the Chinn-Ito index), oil price, financial development and exchange rate. The autoregressive distributed lag (ARDL) approach to cointegration and error correction modeling was employed for the analysis. The empirical evidence indicates that trade openness and financial openness exacerbate output growth volatility in Nigeria in the long run. Favourable crude oil price is found to play significant role in stabilizing output growth in the long run. However, the short run effect of trade openness on growth volatility is negative, implying that in the short run trade openness plays some role in reducing output growth volatility. The short run effect of financial openness on output growth volatility is also negative, but not statistically significant. Further evidence from the study is that financial development and currency depreciation also reduce growth volatility in the short run. Based on the empirical evidence, the paper recommends, as measures to reduce output growth volatility (or stabilize output growth) in Nigeria, cautious liberalization of the nation’s economy, efforts by the government to develop the nation’s financial system to expand its credit extension/provision capacity, and prevention (by the monetary authority) using appropriate policy actions, of undue appreciation of the domestic currency (the naira).