This study investigated the nanofiltration (NF) fouling behavior by two surface waters that serve as source waters for full-scale integrated membrane systems (IMS) of the Tatamagouche and Collins Park drinking water treatment plants (WTPs) in Nova Scotia, Canada. Bench-scale NF fouling experiments conducted under controlled laboratory conditions showed a flux decline of 25% with the Collins Park source water compared with a flux decline of 15% with the Tatamagouche source water over 96 hours of operation. The higher rate of flux decline observed was related to the water quality parameters observed in the Collins Park source water. Membrane autopsies were conducted on virgin and fouled membranes using different techniques to compare the fouling propensity of the two feed waters. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed considerable difference between the fouled membranes fed with two source waters. Analyses of full-scale NF fouling data from the two IMS plants reveal higher fouling in the Collins Park WTP. Full- and bench-scale NF fouling observations provide consistent results that together support ongoing membrane cleaning practices in the Collins Park WTP.