When The Miracle Worker first opened on Broadway on October 19,1959, it was an instant popular success. Despite mixed reviews from the press, it had no trouble attracting 1,000 theatergoers a night during the length of its run. The Miracle Worker was William Gibson's second play to be produced on Broadway, and because of its success with the public, it is also the play for which he is best known and the one on which his reputation as a playwright rests.

The positive critiques of The Miracle Worker focus mostly on Gibson's honest and unsentimental treatment of the relationship between Helen and Annie. Gibson is praised for the wit and humor that he brings to the situation, and for the emotional purity with which he endows the struggle to bring Helen into the world around her by teaching her language. Much has been written about the acting out of the play's youthfulness and vigor by Anne Bancroft, who played Annie Sullivan, and Patty Duke, who played Helen Keller. Both of these actors were praised for the concentration, stamina, and passion that they brought to the play, especially during the now famous struggle between the two of them in the dining room. Next to the climactic scene by the water pump at the end of the play, this scene in the dining room is the one that critics and theatergoers remember most vividly. The pure, raw emotional energy of this moment in the play can, as critic Richard A. Duprey maintained, ''work marvelous things in the soul." It is this emotional connection with the audience that kept the play well attended during its Broadway run and is largely why it continues to be produced today.

Most of the negative criticism that The Miracle Worker received was concerning the structure of the play itself. Critics expressed that what was characterized as an uneven and clumsy structure was a result of the play's adaptation from a television script. Some critics went as far as to say that Gibson sometimes confuses play writing with psychological counseling and although emotionally rewarding, The Miracle Worker is a less than perfect drama. Gibson's use of offstage voices came under fire from some critics as well. These criticisms of the structure of the play, however, never seem to come without praise of other areas of Gibson's talent. In Richard Hayes's review of The Miracle Worker in Commonweal, he praised the play's "affirmations of the human spirit," but declared: "One recognizes the content of the moment, of the experience, but is released into nothing else: essentially, it is a fact to which one has responded. That the fact may be a gratifying demonstration of human worth is, in itself, aesthetically irrelevant.'' Other critics echoed Hayes's sentiments, arguing that although it offers an emotionally satisfying night of theatre, The Miracle Worker does little to further the artistic development of drama as a genre.

Overall, the popular success and positive criticism of The Miracle Worker have continued to eclipse the negative criticism that it has received, and have helped establish its reputation as a classic American play and one of the most life-affirming dramatic works to come out of the 1950s. Robert Brustein summed up Gibson's positive reputation when he observed in the New Republic that "Gibson possesses substantial literary and dramatic gifts and an integrity of the highest order. In addition, he brings to his works authentic compassion, wit, bite and humor, and a lively, literate prose style equaled by few American dramatists."