Norway international Haaland, 20, scored a 15-minute hat-trick as Dortmund moved second, one point behind Bayern who drew 1-1 with Werder Bremen.
Raphael Guerreiro added a fourth before Haaland completed his side’s scoring.
Brazilian winger Matheus Cunha scored in either half for Hertha.
Manager Lucien Favre gave a senior debut to Youssoufa Moukoko – one day after his 16th birthday – to become the youngest person to ever play a professional match in Germany.
The Cameroon-born German youth international, who has scored 141 goals in 88 youth matches for the club, came on with five minutes remaining.
Moukoko biggest talent in world – Haaland
The in-form Haaland has hit 10 goals in his past six games in all competitions for Dortmund and has scored 21 times in 17 matches for club and country this season.
He won the 2020 Golden Boy award for the best under-21 player playing in a European country’s top division earlier on Saturday, finishing ahead of Barcelona and Spain’s Ansu Fati and Bayern Munich’s Canadian left-back Alphonso Davies.
However, after the game Haaland was keen to praise Moukoko and suggested there are big things to come from the teenager.
“I would love to play alongside him,” said the Norway international.
“I think he’s the biggest talent in the world right now. He’s 16 years and one day old, that’s amazing. He has a big career ahead of him. We’re lucky to have him.”
Dortmund were beaten 3-2 by champions Bayern Munich prior to the international break and trailed at half-time to Cunha’s stunning strike from 20 yards.
Haaland levelled two minutes into the second half, sweeping in Emre Can’s pass, and raced clear to add his second two minutes later. He rounded the goalkeeper for his third while his fourth arrived from a Jude Bellingham assist after Guerreiro’s contribution.
Cunha had converted a 79th-minute penalty to make it 4-2, but Dortmund scored swiftly after the restart.
Dortmund return to Champions League action on Tuesday, when they host Club Bruges (20:00 GMT).