The presidential hopeful this month got a response from the Department of Health and Human Services to a letter he and 34 other senators sent this fall calling for an investigation.
The Kentucky Republican's Senate office on Tuesday released the letter from HHS, which pledges to look into the federal government's practices and rules around grants for fetal tissue research.
The issue has been front and center for Republicans since this summer, when a group began releasing undercover videos painting health and abortion provider Planned Parenthood in a negative light. One of the videos depicted a Planned Parenthood official in a conversation about donating tissue from aborted fetuses, with a discussion of compensation.
Several GOP candidates, particularly Carly Fiorina, have made the videos a part of their campaigns, and Congress has also served as a venue for Republicans to attack Planned Parenthood.
In the letter to Paul, the HHS inspector general pledged to interview HHS and the National Institutes of Health to gather information on policies regarding fetal tissue research.
"Our goal is to obtain information related to fetal tissue research grants, NIH's monitoring procedures over third-party certifications and those related to the department's internal fetal tissue research, and any known violations of federal requirements," Daniel Levinson wrote to Paul.
Paul said he was "encouraged" by the action to look into "unconscionable practices" by Planned Parenthood.
"Planned Parenthood selling body parts of the unborn demonstrates that the organization deserves not one penny more of our taxpayer dollars, and I am confident this investigation will give further proof of that," Paul said in a statement.
Planned Parenthood also said Tuesday it welcomed the move, saying it is long past time to review practices around tissue donation.
"This work is often critical to life-saving medical research, and has helped with important breakthroughs, such as the polio vaccine and research into a cure for Alzheimer's disease," said Planned Parenthood Executive Vice President Dawn Laguens. "As we have made clear from the beginning, Planned Parenthood has never sold fetal tissue for profit."
Also Tuesday, House Speaker Paul Ryan pledged to move forward with efforts to strip Planned Parenthood of federal funding when Congress returns from recess in January.
He told conservative radio host Bill Bennett that the House did not defund Planned Parenthood in the government spending bill signed last week because it would have been blocked in the Senate.
"So we have Planned Parenthood defunded in the reconciliation bill. You can use this bill once a year and we used it for this," Ryan said of a congressional maneuver on legislation that will be taken up in January.