The then-untitled 12-year old Karthikeyan scored 5.5/9 at Hastings Congress 2011-2012 (2011), achieving a plus score of +1 =3 against the 4 IMs he faced (the win being against the Frenchman Maxence Godard). At the 10th Parsvnath International Open held in Delhi in January 2012, he scored 7.5/11 recording a plus score against 3 GMs also against 3 IMs, scoring +1 =2 against each group. His GM scalp was Richard Bitoon while his sole loss was to Bhave Kaushik (rated 1868). Good results in the National Team Championships (4/8) in February and in the 14th Dubai Open (2012) (5/9) boosted his rating further. He scored his 1st IM norm at the Orissa GM Open in May 2012. In June 2012, he came =1st in the Asian Youth Chess Championships 2012 Under 14 Open. He scored his 2nd IM norm at the Al Ain Classic and World Cities in December 2012 and his 3rd IM norm at the 11th Delhi International Open in January 2013, achieving his 2400 rating at the same time. He placed =1st alongside Ghosh Diptayan in the Indian National Sub-Junior Championship held in West Bengal in August 2013, scoring 9/11. He placed =7th with 7/10 at the Delhi Open in January 2014.

He is the second player born in 1999 to have won an IM title, the first being Wei Yi (now a GM).