Feghouli has scored 11 goals in 42 appearances for Algeria including a goal in the 2014 World Cup in Brazil which helped his country advance to the last 16.
Medjani, 31, who has 54 caps and plays in Spain for Leganes, is absent for the first time since the 2010 World Cup in South Africa.
Leekens' forward line includes strikers Riyad Mahrez and Islam Slimani -- winners of the English Premier League title with Leicester -- and Dinamo Zagreb's Hillal El Arabi Soudani, the top scorer in Cup qualifiers with seven goals in six matches.
The Africa Cup of Nations takes place in Gabon from January 14 to February
5 with Algeria -- the 1990 winners -- in a tough group alongside Tunisia, Senegal and Zimbabwe.
Goalkeepers: Raïs Ouhab M'bolhi (Antalyaspor, Turkey), Malik Asselah (JS Kabylie), Chemseddine Rahmani (MO Bejaia)
Defenders: Mokhtar Belkhiter (Club Africain, Tunisia), Mohamed Rabie Meftah (USM Alger), Aïssa Mandi (Real Betis, Spain), Hicham Belkaroui (Esperance Tunis, Tunisia), Liassine Cadamuro (Servette, Switzerland), Mohamed Benyahia (USM Alger), Ramy Bensebaïni (Rennes, France), Faouzi Ghoulam (Napoli, Italy), Djamel Eddine Mesbah (Crotone, Italy)
Midfielders: Adlène Guedioura (Watford, England), Saphir Taïder (Bologne, Italy), Nabil Bentaleb (Schalke 04, Germany), Mehdi Abeid (Dijon, France), Yassine Brahimi (FC Porto, Portugal), Rachid Ghezzal (Lyon, France)
Strikers: Islam Slimani (Leicester, England), Riyad Mahrez (Leicester, England), Hillal El Arabi Soudani (Dinamo Zagreb, Croatia), Baghdad Bounedjah (Al Sadd, Qatar), Sofiane Hanni (Anderlecht, Belgium)