In 2005–2006 Bezdenezhnykh worked as a jurist in timber trading company LLP "Alkuma", which was owned by Khabarovsk LDPR leader Sergey Furgal.

[5] In 2010 Bezdenezhnykh ran for Khabarovsk Krai Legislative Duma as No.3 in LPDR party list's Industrial territorial group and in Promyshlenny constituency No.5.

[11] Sergey Bezdenezhnykh ran for re-election to the Legislative Duma in 2019 in the newly created suburban Topolevsky constituency No.4 in Khabarovsky District.

Bezdenezhnykh won the election with 46.74% of the vote, defeating Chairman of the Khabarovsky District Assembly of Deputies Dmitry Savchenko (United Russia, 21.56%) and three other candidates.

[13] Initially, Legislative Duma of Khabarovsk Krai chose Dmitry Priyatnov (LDPR) as its next Representative in the Federation Council, who would replace longtime Senator Viktor Ozerov.

On 4 December Bezdenezhnykh was elected as Senator from Khabarovsk Krai with 24 votes, including Vice Speaker from United Russia Gennady Maltsev.

Senator Bezdenezhnykh publicly named Degtyarev a "temporary figure" and confirmed LDPR's support of Sergey Furgal.

A new coordinating council of the regional office was elected but both senators Sergey Bezdenezhnykh and Yelena Greshnyakova were not nominated and lost their position in party's leadership.

[18] In May 2021 Sergey Bezdenezhnykh left Liberal Democratic Party of Russia due to Degtyarev's ban on support of arrested Governor Furgal.

Bezdenezhnykh ultimately declined to run and endorsed Yelena Greshnyakova who also considered to mount a "Pro-Furgal" challenge to acting Governor Mikhail Degtyarev.

[22] On 15 December 2021 Bezdenezhnykh was among 4 senators to vote against the bill "On common principles of public authority in subjects of the Russian Federation".

Despite being elected to the Legislative Duma Bezdenezhnykh had slim chances to retain his seat in the Federation Council as United Russia received an overwhelming majority.

On September 26, 2024, Legislative Duma unanimously voted for United Russia member Viktor Kalashnikov to replace Bezdenezhnykh in the Federation Council.

[33] For the same reason he was also put under sanctions by the European Union, Canada, Switzerland, Australia, Ukraine, and the United States of America.