Kernes was born into a Jewish family, to Adolf Lazarevych Kernes and Anna Abramovna in Kharkiv. He graduated from the National University "Yaroslav the Wise Law Academy of Ukraine" with a degree in jurisprudence and from Kharkiv National University of Economics with a degree in state management. Between 1977 and 1979 Kernes studied in CTC-14 in Kharkiv and specialised in draftsman-designer on mechanics.
From 1979 to 1990, Kernes worked for a number of enterprises. According to his official biography his career began in 1977. Kernes managed the production and trading company Acceptor from 1992 to 1994. He then became the chairman at CJSC NPK-Holding until 1999. Kernes was then first deputy director of the Kharkiv branch of the Trading House Gas of Ukraine till 2001. He then became CEO at NPK-Holding till 2006.
Prior to his career in politics, Kernes allegedly acted as an organized crime boss in the Kharkiv region, a claim he has denied.
Kernes has a criminal record for theft and fraud; according to him the accusations were "partly fabricated" by "his enemies".
In 1986 he was charged but not prosecuted. In August 1992 Kernes was sentenced by the Kharkiv Regional Court to three years in a penal colony; but the court released him from custody, taking into account that Kernes was held in jail during the criminal investigation that had lasted more than two years. He has been described as a "mini-oligarch", having acquired enough wealth in his business career to launch a career in politics.
In 1998 Kernes was first elected into the Kharkiv city council and has served three terms there. Between April and May 2002 Kernes was the secretary of Kharkiv City Council.
In November 2004 he supported the Orange Revolution. He came out to condemn the actions taken by the regional governor Yevhen Kushnaryov. In 2006 he was elected to the Kharkiv City Council on the list of the Party of Regions, as member of the party. In April 2006 Kernes became the secretary of Kharkiv City Council.
Since 2010 after Mikhail Dobkin had been appointed to the post of the head of the Kharkiv regional state administration, Kernes had been the secretary of city council, the acting mayor of Kharkiv (March 2010 – 24 November 2010). In 2010 had his candidacy nominated for the Party of Regions in the elections to local authorities. In November Kernes was elected as the mayor of Kharkiv with a small, controversial margin. On 24 November 2010 he took the oath and entered the post in early December 2010.
In January 2014, Kernes controversially awarded himself a 25% pay raise.
Kernes was noted for holding a strongly 'pro-Russian' stance and for being a supporter of the former Ukrainian President Viktor Yanukovych. During the anti-Yanukovych Euromaidan protests in late 2013 and early 2014, he was accused of organizing Antimaidan demonstrations, as well as hiring titushky (thugs that allegedly provocated and attacked Euromaidan supporters).
Following the ousting of Yanukovych in February 2014, and after he and the governor of Kharkiv Oblast, Mykhailo Dobkin, had briefly found refuge in Russia, Kernes was accused of alleged connections to death threats, kidnapping and torturing of participants of Euromaidan in Kharkiv and was subsequently placed under night-time house arrest. This criminal case against him was dropped on 30 July 2014 "due to the serious illness of the suspect". He was accused, in February 2014, by the then (more pro-Western) new Ukrainian leadership of promoting separatism. However, since then he is believed to have softened this position. In March 2014 he stated that he had been a "prisoner of Yanukovych's system" and that he expected "good things to come" from the new Yatsenyuk Government.
On 28 April 2014, Kernes was shot once in the back while biking by an unknown assailant using a sniper rifle.
Although the wound was life-threatening, doctors performed emergency surgery and were able to stabilize him. The following day Kernes was flown to Israel for further treatment. According to a report by Televiziyna Sluzhba Novyn on 10 May 2014, he was "making a quick recovery"; in the accompanying interview he stated "I'm in favor of Kharkiv remaining part of Ukraine and therefore in favor of seeing her flourish". (While recovering in Israel) Kernes stated on 11 June 2014 that his willingness to cooperate with the (then just inaugurated) Ukrainian President Petro Poroshenko. On 12 August 2014 he stated "Please remember these people—Kharkiv was, is and will be part of a single and indivisible Ukraine". Kernes commented on the 2014 Russian annexation of Crimea on 23 August 2014 saying "Crimea will return to Ukraine, I believe in it". Kernes returned to Kharkiv on 17 June 2014. Since then he is using a wheelchair.
In the October 2015 Kharkiv mayoral election Kernes was re-elected as a candidate of Revival in the first round of the election with 65.8% of the votes, with a voter turnout of 44.4%.
Kernes is married to his second wife, Oksana (née Haysinskaya). Kernes' first wife was Oksana Vasilenko; the couple divorced in 1985. Kernes is a father of three children, including his stepson, Haysinskaya's son from her previous marriage. Kernes' first son was born in his marriage to Vasilenko, and his second son was from Halina Privalov, with whom he had an affair between his first and second marriage. In January 2003 Haysinskaya appealed to the police department that Kernes had caused her injuries. After that, Kharkiv billboards appeared with the message "Oksana, I'm sorry!".
Kernes owns 27 dogs, assorted birds, and other animals and since 2007 has lived in a Kharkiv hotel. His Instagram account has been described by The New York Times as "eccentric"; Kernes has claimed "Of all the mayors, my Instagram account is the best". He is known for actively promoting healthier living.
Since they met in 1998, Kernes has been a close friend of Mykhailo Dobkin – governor of Kharkiv Oblast from 2010 to 2014, mayor of Kharkiv from 2006 to 2010, past and current member (currently for Opposition Bloc) of the Verkhovna Rada (Ukraine's parliament) and the Party of Regions candidate in the 2014 Ukrainian presidential election.
In line with new anti-corruption rules, which compel all senior public officials to declare their wealth in an electronic database, Kernes declared in October 2016 that he owned more than $1.6m in hard currency.
Kernes is widely known as "Gepa" (Ukrainian: Гепа – ass, butt).The Order of Merit third class (5 July 2012) – For the significant personal contribution to the preparation and conduct of the 2012 UEFA European Football Championship final in Ukraine, successful implementation of infrastructural projects, law and order and public safety guarantee during the tournament, improvement of international Ukraine authority, high professionalism.
The Kharkiv regional state administration certificate.
The Badge of Honor 'Slobozhyanskaya Slava', "For diligence to 350 years of Kharkiv foundation"
The Kharkiv City Council Executive Committee certificate.
Kharkiv and Bohodukhov Metropolitan Nicodemus certificate.
The Order of Glory to the Loyalty to the Fatherland, III class.
The Medal '60th anniversary of the Battle of Kursk'.
The Medal 'For active participation in the veteran's movement'.
The Order of Glory to the Loyalty to the Fatherland.
The XVII annual award 'Person of the Year 2012' in the category of 'City Head of the Year'.