Recent research brings diverse findings on timing of the second demographic transition (SDT) in Serbia, mostly based on regional divergence of demographic trends. SDT in European context was studied using different socio-demographic indicators, but rarely at sub-national levels. Consequently, main aim of the paper is to explore trends in non-marital births at lower spatial level in Serbia using appropriate spatial autocorrelation statistics. Besides, it was of particular interest to inspect developments of this SDT indicator in Serbia with respect to other former communist countries given known skepticism relating to the diffusion of the process to the East. Even if the share of non-marital births has been raised from 8% in 1950 to about 24% in 2011, the position of Serbia as regards this indicator has changed downwards in the European context during the last 60 years. From the regional aspect, we show that east Serbia stands quite distinctively out from the rest of the country in terms of both highest share of non-marital births (>50% in most municipalities) and its recent rise. The local Moran’s I statistics of the indicator for the period between the census years of 2002 and 2011 denoted two clusters which represent two distinctively different areas of the country: more developed west including the largest urban centers (the lowest share of non-marital births and its change over the period) and less developed east (highest share of non-marital births and its highest increase). This is much in line with findings relating to SDT in most of post-socialist societies in Europe in the sense that higher shares of non-marital births refer mainly to pre-marital cohabitations or single mothers and are more common among persons at lower social strata due to rationally developed strategies in overcoming structural risks associated with family change in low fertility regime.