The Belgium international was due to meet fans during an event at Everton Two in the city centre yesterday, but the club were forced to call it off due to "unforeseen circumstances".
Shortly after the announcement, Fellaini wrote on Twitter: "Sorry to the Everton fans, I cannot make the signing session this afternoon. Will do another one soon. Felly."
The decision has sparked questions over Fellaini's future at the Merseyside club.