The 19-year-old man handed himself into a police station in Staffordshire yesterday, where he was arrested on suspicion of computer misuse offences.
He has been bailed until a date in late May, Scotland Yard revealed.
A warrant was executed at an address in the area in connection with the investigation.
This is the sixth arrest relating to the TalkTalk incident last October, and the second in Staffordshire.
More than 150,000 customers were affected in the data breach, which saw what police described at the time as a 'significant and sustained cyber-attack' on the internet provider's website.
The hack, it was revealed earlier this year, had cost the company around £60 million and led to the loss of more than 100,000 customers in the three months afterwards.
Initially TalkTalk warned that all customers had potentially been affected, but data had only leaked regarding around four per cent of their total consumer base.
So far, all of the arrests related to the data leak have been of people under the age of 21.
The first arrests came within days of the hack.
A 15-year-old boy was arrested on October 26 in Northern Ireland and bailed to return pending further enquiries. Three days later, a 16-year-old boy was arrested in Feltham and is currently on bail.
The third was arrested in Staffordshire on October 31. The 20-year-old was arrested on suspicion of Computer Misuse Act offences. He returned on bail this month and has been re-bailed to a date in mid-June.
In November, a 16-year-old boy was arrested in Norwich under the Computer Misuse Act and an 18-year-old man was arrested in Llanelli, Wales on suspicion of blackmail. They have both been bailed.
The investigation, police say, is still ongoing.
Those that believe they have been affected by the alleged data theft should visit help2.talktalk.co.uk/oct22incident
More information regarding the incident can be found on the Action Fraud website at actionfraud.police.uk/news