<p>The feasibility of using artificial seawater (ASW) instead of fresh water as the medium for reactive dyeing of cotton fabric is investigated in this study. A number of dyes of different reactive groups are used. Cotton fabrics are dyed in ASW media with (ASW+) or without (ASW−) further addition of NaCl and their dyeing, colourfastness, surface and physical properties are examined and compared with cotton fabrics dyed in deionised (DI) and distilled (DIS) water media. Although nearly all ASW dyed fabrics obtain lower colour yield (0.7–65.2% lower) than that of DI and DIS dyed fabric, the results of this work reveal that triazine-based reactive dyes disfavour cotton dyeing in DIS and ASW (ASW− and ASW+) media (0.2–65.2% lower) while fluorochloropyrimidine (FCP)-based and dichlorochinoxaline (DCC)-based monofunctional reactive dyes in DIS and ASW dyeing system offer better colour yield (5.8–72.5% higher). The pH value and salinity of the dyebath in those four different dyeing media are measured. The reflectance curves, CIE L*a*b* value, colour evenness, fastness, surface, fastness and tensile properties of the dyed cotton fabrics are evaluated. The findings verify that the use of ASW does not alter the colour properties of the dyed specimens. Both DI, DIS and ASW dyed specimens reflect good to excellent colour levelness (0.01–0.46) and fair to excellent washing, crocking and perspiration fastness properties (rating 3–4 to 5) without any significant fibre damage while both exhibit lower breaking strength and extension after the dyeing process when compared with pristine undyed cotton fabric.</p>