Mariska Hargitay and Jayne Mansfield

It might be argued that Hollywood sex symbol Jayne Mansfield is more famous now for being the mother of Mariska Hargitay than for her own status as a prototypical ’50s bombshell and star of such films as “The Girl Can’t Help It.” Ms. Hargitay’s tenure as Olivia Benson on “Law and Order: SVU,” after all, has lasted twice as long as her mother’s entire film career.

But Mansfield, who died in a violent car crash in 1967, does occupy a singular if amorphous place in the pop-culture pantheon, and Ms. Hargitay’s mission as director and producer of “My Mom Jayne” is multifold: rehabilitate her mother’s reputation as one of the “dumb blondes” who rode the wake of Marilyn Monroe (Diana Dors and Mamie Van Doren were others); examine Mansfield as an example of manufactured Hollywood product; and come to grips with her own trauma concerning parentage and inheritance. It is a very personal documentary, a designation that can connote the good, the not-so-bad and the distinctly uncomfortable. “My Mom Jayne” has it all, including a puzzle that Ms. Hargitay pursues throughout.

Ms. Hargitay

Revealing the payoff, such as it is, to “My Mom Jayne” would be a spoiler, though it seems to be common knowledge to members of the Mansfield fan base-cum-cult. But even without the family tie, Ms. Hargitay would have a terrific subject on her hands. In the archival interviews used throughout (the editing by J.D. Marlow is first-rate), Mansfield is as open as she can be about having used her “pin-up” assets, as she calls them, to advance her career. She had aspirations to be a serious actress, although it was probably her physical attributes that helped relegate her to the daffy blonde roles for which she was overqualified. She had excelled academically as a young woman, studying languages as well as piano and violin, and we get to see her perform on both during Ms. Hargitay’s film. Do you play well, TV host Jack Paar asks, as Mansfield prepares to perform a short violin piece. “I play,” she responds, a moment that is self-deprecating, deadpan and charming.

Mansfield

Ms. Hargitay was a 3-year-old child when her 34-year-old mother died—a child no one realized at first was tucked in the wreckage of the car, under the passenger seat. (The more gruesome details of the crash, some of which are strictly rumors, are left unaddressed here.) Mansfield was 3 when her own father suffered a fatal heart attack at the wheel, and she, too, was in the car. No one pretends this is some cosmic link between mother and daughter, but Ms. Hargitay looks for connections, because she has no real memories of her mom. Her older half-sister, Jayne Marie, the child of Mansfield’s marriage to publicist Paul Mansfield in 1950, provides far more in terms of real-time recollections of Jayne, as do Ms. Hargitay’s older brothers, Miklós and Zoltán, whose father was Hungarian athlete and bodybuilder Mickey Hargitay, easily the most sympathetic character in the entire film.

At about two hours, “My Mom Jayne” feels a bit bloated, with the emotional beats played too long and too often and being a bit obvious besides. Ms. Hargitay also treats her mother’s story like a mystery when it was really anything but—Mansfield knew what she had, used it to her best advantage, was nobody’s fool, liked men enough to marry three times if not always wisely, and was willing to play her personal life out in tabloid headlines if it served her aims as an actress. That she left her daughter with a messy legacy is unquestionable, as is the fact that she never freed herself from the stereotypes connected to being blond, built and beautiful. But it could also be argued that she never really got the chance.

My Mom Jayne

Friday, 8 p.m., HBO

Mr. Anderson is the Journal’s TV critic.