The FIFA Arab Cup will run from 30 November to 18 December in Doha. Queiroz revealed Ashour's replacement in a press conference in Cairo ahead of travelling to Doha later on Saturday.
The 30-year old Hegazi, who was previously called up in the preliminary squad for the tournament, will replace Ashour, 23, who was dropped out from the squad on Friday after testing positive for coronavirus.
Egypt were drawn in Group D of the FIFA Arab Cup alongside Algeria and the winners of the games between Libya and Sudan, and Lebanon and Djibouti.
In its opening game, Egypt will play against Lebanon on Wednesday.
Last week, Queiroz, who has been appointed in September, announced the final 23-man squad for the tournament seen as a dress rehearsal for next year's World Cup finals, which will also be hosted in Qatar.
The Portuguese coach didn't call any of the foreign-based players in the Arab Cup squad, with the tournament falling outside of the normal international calendar.
The Arab Cup comprises 23 Arab nations, including several North African and Asian heavyweights, such as Algeria, Morocco, Tunisia, and Saudi Arabia.
The nine highest-ranked teams were automatically given group-stage spots. They will be joined by the seven winners of the qualifying stage. The top two in each group will advance to the quarter-finals.
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