At the end of the 1950s, Cele Goldsmith took over as editor of both Fantastic and Amazing Stories, and quickly invigorated the magazines, bringing in many new writers and making them, in the words of one science fiction historian, the "best-looking and brightest" magazines in the field. Goldsmith helped to nurture the early careers of writers such as Roger Zelazny and Ursula K. Le Guin, but was unable to increase circulation, and in 1965 the magazines were sold to Sol Cohen, who hired Joseph Wrzos as editor and switched to a reprint-only policy. This was financially successful, but brought Cohen into conflict with the newly formed Science Fiction Writers of America. After a turbulent period at the end of the 1960s, Ted White became editor and the reprints were phased out.
White worked hard to make the magazine successful, introducing artwork from artists who had made their names in comics, and working with new authors such as Gordon Eklund. His budget for fiction was low, but he was occasionally able to find good stories from well-known writers that had been rejected by other markets. Circulation continued to decline, however, and in 1978, Cohen sold out his half of the business to his partner, Arthur Bernhard. White resigned shortly afterwards, and was replaced by Elinor Mavor, but within two years Bernhard decided to close down Fantastic, merging it with Amazing Stories, which had always enjoyed a slightly higher circulation.
In 1938, Ziff Davis, a Chicago-based publisher looking to expand into the pulp magazine market, acquired Amazing Stories. The number of science fiction magazines grew quickly, and several new titles appeared over the next few years, among them Fantastic Adventures, which was launched by Ziff Davis in 1939 as a companion to Amazing. Under the editorship of Raymond Palmer, the magazines were reasonably successful but published poor-quality work; when Howard Browne took over as editor of Amazing in January 1950, he decided to try to move the magazine upmarket. Ziff Davis agreed to back the new magazine, and Browne put together a sample copy, but, when the Korean War broke out, Ziff Davis cut their budgets and the project was abandoned. Browne did not give up, and in 1952 received the go-ahead to try a new magazine instead, focused on high-quality fantasy, a genre which had recently become more popular. The first issue of Fantastic, dated Summer 1952, appeared on March 21 of that year.
Sales were very good, and Ziff Davis was sufficiently impressed after only two issues to move the magazine from a quarterly to a bimonthly schedule, and to switch Amazing from pulp format to digest-size to match Fantastic. Shortly afterwards the decision was taken to eliminate Fantastic Adventures: the March 1953 issue was the last, and the May–June 1953 issue of Fantastic added a mention of Fantastic Adventures to the masthead, though this ceased with the following issue. Payment started at two cents per word for all rights, but could go up to ten cents at the editor's discretion; this put Fantastic in the second echelon of magazines, behind titles such as Astounding and Galaxy. The experiment with quality fiction did not last. Circulation dropped, which led to budget cuts, and in turn the quality of the fiction fell. Browne had wanted to separate Fantastic from Amazing's pulp roots, but now found he had to print more science fiction (sf) and less fantasy in order to attract Amazing's readers to its sister magazine. Fantastic's poor results were probably a consequence of an overloaded sf-magazine market: far more magazines appeared in the early 1950s than the market was able to support. Ziff Davis sales staff were able to help sell Fantastic and Amazing along with the technical magazines that it published, and the availability of a national sales network, even though it was not focused solely on Fantastic, undoubtedly helped the magazine to survive.
In May 1956, Browne left Ziff Davis to become a screenwriter. Paul W. Fairman took over as editor of both Fantastic and Amazing. In 1957, Bernard Davis left Ziff Davis; it had been Davis who had suggested the acquisition of Amazing in 1939, and he had stayed involved with the sf magazines throughout the time he spent there. With his departure Amazing and Fantastic stagnated; they were still issued monthly, but drew no attention from the management of Ziff Davis.