The governing body last month confirmed that it was looking into an incident involving full-back Hardaker, who was given a five-match ban in June for homophobic abuse of a referee, during the Rhinos' 13-12 loss to St Helens on August 29.
The latest probe was said to relate to comments made towards Saints second-rower Mark Flanagan.
But England international Hardaker is now free to play in Leeds' play-off clash with the Catalan Dragons on Saturday after the RFL's Match Review Panel determined that there was insufficient evidence for the 22-year-old to be charged.
An RFL statement read: "The RFL can confirm that no further action will be taken following an investigation into an incident in the First Utility Super League fixture, Leeds Rhinos v St Helens played on Friday August 29.
"Details of the investigation were presented to the RFL Match Review Panel which concluded that there was insufficient evidence for charges to be brought."
Rhinos chief executive Gary Hetherington had slammed the RFL for conducting a "witch-hunt" against Hardaker before the player on Monday expressed his frustration at the uncertainty surrounding him, revealing that the allegations were also affecting his family.
Hardaker was named in the 2014 Super League Dream Team on Monday.