Striker Mohamed Nagy - known as Gedo in Egypt - and the versatile Ahmed Fathi will also join the club on loan until the summer from Al-Ahly.
Gedo has scored 17 goals in 32 international appearances and won the golden boot when Egypt won the Africa Cup of Nations.
Fathi has played in England before - a short spell with Sheffield United back in 2007 - and he and Gedu helped Al-Ahly win the 2012 CAF Champions League.
Elmohamady, 24, is returning to Hull after an outstanding spell for Steve Bruce's team earlier this season when he played 23 times.
He did initially join the Tigers on a season-long loan but Sunderland had the right to recall him, and they did just that earlier in January when they had a number of players out injured.
Sunderland boss Martin O'Neill has however decided he will not need him again this season and allowed him to rejoin Hull's bid for promotion back to the Premier League.