A device for monitoring fluid leakage. A flexible plastic sheet (11) is provided with a tear-off strip (12), which divides the sheet in a first sheet portion (21) and a second sheet portion (20) and forms a folding line. An adhesive (22) is arranged at the first portion (21). The sheet is folded along the folding line and the first portion is attached to the second portion via the adhesive to form a pocket along the folding line for enclosing a connector and hose assembly to be monitored. An optical sensor having an absorbent pad and an optical fiber is enclosed in said pocket when formed. The exterior end of the optical fiber is connected to an optical detector device for monitoring if the interior end of the optical fiber comes into contact with a fluid, indicating a leakage of the connector.