A method for monitoring an ignition system (56) including a spark plug (30) of an internal combustion engine (1) is disclosed. The method comprises determining (108) an operation value (CR) associatedwith an electrical parameter indicative of an operation of the ignition system (56) during actuation of the spark plug (30). The method further comprises determining (106) at least one parameter indicative of a current engine operation condition of the internal combustion engine (1), and determining (116) a current spark plug state of the spark plug (30) based on the at least one engine parameterand the operation value (CR) associated with the electrical parameter of the ignition system (56).