Lewis said this is in line with the UK's right to do so under the EU treaties, despite the outcome of the EU referendum on 23 June which will see the UK leave the EU.
He said continued membership of the agency was important in tackling online terrorism propaganda and cybercrime.
Based in The Hague, Europol is an agency which aims to strengthen and facilitate cooperation in preventing serious crimes and combatting organised crime, in particular where the crimes affect two or more member states.
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The UK has been a member of the agency since its creation in 1998 and chose to opt-in in 2014 when the UK negotiated the right to choose which justice and home affairs matters to be part of.
Speaking on Monday, Lewis, said, "The UK is leaving the EU but the reality of cross-border crime remains. Europol provides a valuable service to the UK and opting in would enable us to maintain our current access to the agency, until we leave the EU, helping keep the people of Britain safe."
He added, "We now await the outcome of the scrutiny process."
The opt-in decision will be discussed by the UK's House of Commons and House of Lords EU scrutiny committee.
Meanwhile, in a speech on Monday, UK Prime Minister Theresa May said, "As we leave the EU, we will also use the strength and size of our economy to lead the way in getting out into the world and doing new business with old allies and new partners alike.
"We will use the freedoms that come from negotiating with partners directly, to be flexible, to set our own rules and forge new and dynamic trading agreements that work for the whole UK."
However, she added, "We can't deny that there have been downsides to globalisation in recent years, and that in our zeal and enthusiasm to promote this agenda as the answer to all our ills we have on occasion overlooked the impact on those closer to home who see these forces in a different light."
She denied that the UK government was pursuing an anti-business agenda, saying, "Asking business to work with government to play its part is profoundly pro-business, because it is fundamental to retaining faith in capitalism and free markets."