Dortmund, who came under heavy criticism after throwing away a 2-0 lead in the 88th minute to lose 3-2 against Werder Bremen last Saturday, endured a nervy end to the match but held on to record their third win of the season.
Modeste headed in a cross from Salih Ozcan, who also arrived from Cologne this summer, in the 32nd minute to put Dortmund 1-0 up.
Modeste, who is better known for his theatrical celebrations which often involve dancing and even props, ran emotionally to Dortmund manager Edin Terzic and embraced him after scoring.
The goal was Modeste’s eighth against Hertha in 11 appearances.
Dortmund have now scored 10 goals in competitive fixtures this season, each of which has come from a different scorer.
Elsewhere, Union Berlin sit alone on top of the table, at least until Saturday’s late game, after a 6-1 win away at Schalke.
Braces from Sheraldo Becker and Sven Michel, along with strikes from Morten Thorsby and Janik Haberer saw Union record a dominant victory.
The Berlin club, who will begin their first ever Europa League campaign in September, are unbeaten (four wins and a draw) after five competitive games in 2022-23.
RB Leipzig got their first Bundesliga win of the season with a 2-0 home victory over Wolfsburg.
Leipzig’s French forward Christopher Nkunku converted a penalty after five minutes to open the scoring.
Former Chelsea striker Timo Werner, who started from the bench due to an infection, set up Nkunku’s second in the 90th minute to relieve some pressure from Leipzig coach Domenico Tedesco.
Bayer Leverkusen picked up their first points of the season with a dominant 3-0 win away at Mainz.
Leverkusen, who had scored just one goal in three Bundesliga games this season and have already been eliminated from the German Cup, scored three first-half goals, including a brace for Dutch wing back Jeremie Frimpong.
In Sinsheim, Hoffenheim won their third game of the season with a hard-fought 1-0 victory over Augsburg, thanks to a first-half goal from Dennis Geiger.
In Saturday’s late game, Bayern Munich have the chance to reclaim their place at the top of the table if they beat the visiting Borussia Moenchengladbach.