The purpose of this study is to assess the effect of tavapadon on the change from baseline in total daily hours of "on" time without troublesome dyskinesia in L-Dopa-treated participants with Parkinson's Disease (PD) who are experiencing motor fluctuations.

Key Inclusion Criteria:

• Male and female participants aged 40 to 80 years, inclusive, at the time of signing the informed consent form (ICF).
• Sexually active men or women of childbearing potential must agree to use acceptable (at minimum) or highly effective birth control, or remain abstinent during the trial and for 4 weeks after the last dose of trial treatment.
• Participants who are capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the ICF and in this protocol.
• Participants with a diagnosis of PD that is consistent with the UK Parkinson's Disease Society Brain Bank diagnostic criteria, with bradykinesia and motor asymmetry.
• Participants with modified Hoehn and Yahr stage 2, 2.5, or 3 in the "on" state.
• Participants with a good response to levodopa (L- Dopa) in the judgment of the investigator.
• Participants who return a completed self-reported home diary for motor function status (Hauser diary) during the screening period (after diary training and concordance testing has occurred), with recordings for 2 consecutive days (ie, 2 consecutive 24-hour periods) showing at least 2 and half hours of "off" time on each of the 2 days.
• Participants who are on a stable dose of L-Dopa for at least 4 weeks prior to screening and are taking a minimum total daily dose of 400 milligram (mg) divided in at least 4 doses per day of standard carbidopa/levodopa or divided in at least 3 doses per day of extended-release carbidopa/levodopa capsules. The carbidopa/levodopa dose and frequency must be maintained for the duration of the trial.
• Prior and concurrent use of catechol-O-methyltransferase (COMT) inhibitors, monoamine oxidaseB (MAO-B) inhibitors, amantadine, istradefylline or anticholinergic drugs are permitted if the use was initiated greater than (>) 90 days before the baseline visit and the dosage will remain stable for the duration of the trial (ie, no change in the COMT,MAO-B inhibitor, amantadine, istradefylline or anticholinergic dose is permitted during the trial).

Key Exclusion Criteria:

• Participants with a history or clinical features consistent with essential tremor, atypical or secondary parkinsonian syndrome (including, but not limited to, progressive supranuclear palsy, multiple system atrophy, cortico-basal degeneration, or drug-induced or post stroke parkinsonism).
• Participants with a history of nonresponse or insufficient response to L-Dopa at therapeutic dosages.
• Participants with a history or current diagnosis of a clinically significant impulse control disorder(Disruptive, Impulse Control, and Conduct Disorder per DSM-5).
• Participants with the presence of or history of brain tumor, hospitalization for severe head trauma, epilepsy (as defined by the International League Against Epilepsy), or seizures.
• Participants with a history of psychosis or hallucinations within the previous 12 months.
• Participants who answer "yes" on the Columbia-Suicide Severity Rating Scale (C-SSRS) Suicidal Ideation Item 4 or Item 5 (Active Suicidal Ideation with Some Intent to Act, Without Specific Plan, or Active Suicidal Ideation with Specific Plan and Intent)and whose most recent episode meeting the criteria for C-SSRS Item 4 or Item 5 occurred within the last6 months, OR Participants who answer "yes" on any of the 5 C-SSRS Suicidal Behavior Items (actual attempt, interrupted attempt, aborted attempt, preparatory acts, or behavior) and whose most recent episode meeting the criteria for any of these 5C-SSRS Suicidal Behavior Items occurred within the last 2 years, OR Participants who, in the opinion of the investigator, present a serious risk of suicide.
• Participants with substance abuse or dependence disorder, including alcohol, benzodiazepines, and opioids, but excluding nicotine, within the past 6months (180 days).
• Participants with dementia or cognitive impairment that, in the judgement of the investigator, would exclude the participant from understanding the ICF or participating in the trial.
• Participants with any condition that could possibly affect drug absorption, including bowel resections, bariatric weight loss surgery, or gastrectomy (this does not include gastric banding).
• Participants who have a positive result for human immunodeficiency virus (HIV) antibodies, hepatitis B surface antigen (HbsAg), or hepatitis C virus (HCV)antibodies at screening.
• Participants with a history of myocardial infarction with residual atrial, nodal, or ventricular arrhythmias that are not controlled with medical and/or surgical intervention; second- or third-degree atrioventricular block; sick sinus syndrome; severe or unstable angina; or congestive heart failure within the last 12months. A recent (less than or equal to [<=12]months) history of myocardial infarction with secondary arrhythmias is exclusionary regardless of the therapeutic control.
• Participants with a history of neuroleptic malignant syndrome.
• Participants who are currently receiving moderate or strong CYP3A4 inducers or CYP3A4 inhibitors(except for topical administration).
• Participants with a positive urine drug screen for illicit drugs are excluded and may not be retested or rescreened. Participants with a positive urine drug screen resulting from use of marijuana (any tetrahydrocannabinol-containing product),prescription, or over-the-counter medications or products that, in the investigator's documented opinion, do not signal a clinical condition that would impact the safety of the participant or interpretation of the trial results may continue evaluation for the trial following consultation and approval by the medical monitor
• Participants with a Montreal Cognitive Assessment(MoCA) score <26.
• Participants with clinically significant orthostatic hypotension (eg, syncope).
• Participants with a 12-lead ECG demonstrating aQTcF interval >450 msec.
• Participants with moderate or severe renal impairment (creatinine clearance as estimated by Cockcroft-Gault formula <30 mL/min or on dialysis).
• Participants with any of the following abnormalities in clinical laboratory tests at the Screening Visit, as assessed by the central laboratory and confirmed by a single repeat measurement, if deemed necessary:
• Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) >=3 × Upper Limit Normal (ULN).
• Total bilirubin >=1.5 × ULN. Participants with a history of Gilbert's syndrome may be eligible provided they have a value \