Irina Terentjeva won a silver medal in individual 10 km F event in the 2001 European Youth Championships (EYOF 2001) in Vuokatti, Finland. She won a bronze medal in the individual 5 km F event at the 2002 Junior World Championships in Schonach, Germany.
Terentjeva's best finish at the FIS U23 World Ski Championships was a 7th place in the individual 10 km F event in Tarvisio 2007.
Terentjeva's best finish at the FIS Nordic World Ski Championships was 27th in the individual sprint event at Val di Fiemme in 2003. Terentjeva's best finish at the individual 10 km F event was 30th at the 2007 World Ski Championships in Sapporo.
Her best World Cup finish was 25th at a 10 km event in Finland in 2005. Terentjeva's best position at the individual event 15 km F at the Winter Universiade was a 4th place in Pragelato 2007.
Irina Terentjeva moved to Finland in 2010 and finished her skiing career in 2012.