Dean Witter Reynolds, the brokerage firm recently acquired by Sears, Roebuck & Co., has agreed to pay nearly $2 million to women, blacks and Hispanics who were denied employment or promotion from 1976 to 1981, and to set up a $3 million affirmative-action program to bring women and minorities into the business.

Without admitting that it ever practiced racial or sexual discrimination, Dean Witter agreed to a proposed court order requiring "affirmative action to increase female, black and hispanic employment throughout the work force."

The Equal Employment Opportunity Commission estimates that some 4,000 present and former Dean Witter employes are eligible for payments. Under the settlement, the money is to be distributed to secretaries who were denied promotion to account executive, to "all females, blacks and hispanics who held or sought to hold any managerial or professional position" in the six-year period covered by the suits, and all females, blacks and Hispanics who were turned down for or fired from positions as account executive during that time.

Dean Witter, the nation's fifth-largest brokerage house, has 10,400 employes. Statistics compiled by the EEOC on the racial and sexual composition of Dean Witter's work force have been sealed by a federal judge in Philadelphia, but are expected to be made public when the judge holds a hearing on the settlement in September.

The proposed consent decree, which ends lawsuits against Dean Witter by female employes and by the EEOC, was reached in negotiations over the winter and published in yesterday's Wall Street Journal.

The case began in 1977 when Mary Kay Bartelson, an account executive in Dean Witter's Philadelphia office, sought to become a commodities trader and was fired instead, according to her attorney, Michael D. Buchwach of Pittsburgh.

Bartelson, a white woman, sued, alleging discrimination against females. A federal judge in Philadelphia designated her case a class action, in which she represented all white females who were alleged victims of discrimination, but said she could not represent blacks or Hispanics. The EEOC, which was preparing its own case against Dean Witter, joined the Bartelson case to represent the racial minorities, EEOC lawyer Estelle Franklin said yesterday.

In a related development yesterday, the EEOC announced a $2.3 million out-of-court settlement of a half-dozen sex discrimination lawsuits against Minnesota Mining and Manufacturing Co.

The agreement, which must still be approved by U.S. District Judge Donald D. Alsop of St. Paul, Minn., involves some 2,350 women and would end eight years of litigation.

The settlement involves one individual and five class-action lawsuits that charged 3-M "with sex discrimination in job assignments, wages, promotions, transfers and other terms and conditions of employment," the EEOC said.