Born in New York City, Post grew up in the Coney Island and Sheepshead Bay neighborhoods of Brooklyn and then in The Bronx. In a 1999 interview, he recalled his start in drawing and his father's influence:

As a teenager, Post attended the Hastings School of Animation, in New York City. When he was age 16 or 17, his father was stricken with tuberculosis and hospitalized, making Post the primary breadwinner for a family of four. At Paramount Pictures' animation studio, Famous Studios he earned $24 a week as an in-betweener.

To supplement what even then was considered a meager income, Post broke into comic books...first being rejected by the L.B. Cole studio on 42nd Street and then successfully selling work to artist Bernard Bailey on West 43rd. Post's earliest confirmed comic book art appeared in 1945: the cover of publisher Prize Comics' Wonderland Comics #2, and the five-page "3-Alarm Fire!", starring Hopeless Henry, in Cambridge House Publishers' Gold Medal Comics #1. Credited as Howie Post, he soon began drawing for the company that would become DC Comics, including the features "Jimminy and the Magic Book" in More Fun Comics, "Rodeo Rick" in Western Comics, "Presto Pete" in Animal Antics, "Chick 'n Gumbo" in Funny Folks, and "J. Rufus Lion" in Comic Cavalcade, among other work. During the 1950s, he drew many humorous stories for the satirical comics Crazy, Wild and Riot, from Marvel Comics' 1950s forerunner, Atlas Comics, as well as occasional stories in that publishers horror comics, including Journey into Mystery, Uncanny Tales, and Mystery Tales. As Howie Post, he drew the three-issue run of Atlas' The Monkey and the Bear (Sept. 1953 - Jan. 1954).

By 1961, Post was drawing adventures of such Harvey Comics children's characters as Hot Stuff the Little Devil, Spooky the Tuff Little Ghost, Wendy the Good Little Witch and the Ghostly Trio in such comics books as Casper's Ghostland and TV Casper & Company, starring Casper the Friendly Ghost. Post was the head of Paramount Cartoon Studios, as well as a key director, succeeding Seymour Kneitel from 1964 through 1965.

In the late 1960s, as Howie Post, he created, wrote and drew the prehistoric-teen comic book Anthro for DC Comics, which ran six issues (Aug. 1968 - Aug. 1969) after debuting in Showcase 74, with the last issue in the series inked by Wally Wood and Ralph Reese.

The Dropouts was a comic strip created by Post and was syndicated by United Features Syndicate from 1968 to 1981. Post began the strip at the same time his comic book Anthro was canceled. The premise of The Dropouts was a variation on the "stranded on a desert island" gag. The two main characters, Alf and Sandy, were indeed castaways, but the island is hardly deserted: One of the strips' running gags was how closely the natives' society resembled Western civilization. Other characters, all natives, included a one-man police force, a doctor and a chef running a cafe with inedible food. There were other Western characters, including a religious zealot, an angry feminist and a disheveled alcoholic, Chugalug.

In later years, Post taught art and illustration privately and at New York's School of Visual Arts.

He is survived by his companion of 24 years, Pamela Rutt, and two daughters. His wife Bobbee predeceased him in 1980.