Legal claims had been filed against a doctor who prescribed Prince pain medication and a pharmacy that supplied him with medicine.
Dismissals usually occur after a settlement has been reached, but such agreements often remain confidential.
The 57-year-old died in 2016 after an accidental overdose of the painkiller fentanyl at his home in Minneapolis.
Claims that had been filed against the Walgreens pharmacy chain and Dr Michael Schulenberg, who treated Prince in the weeks before his death, have been dismissed.
The star's family had argued that failures in Dr Schulenberg's treatment played a "substantial part" in his death. Dr Schulenberg denied any wrongdoing.
A claim against the Trinity Medical Center in Illinois, where he was treated for an opioid overdose the week before he died, has also been dismissed.
A lawyer for Prince's estate, John Goetz, told the BBC he could not comment on what led to the cases being dismissed.