Petals of Blood was officially launched by the Kenyan government in July 1977, in a show of the Kenyatta government's commitment to the principles of free speech. However, it was clear that the ruling elite and many members of the upper classes in Kenya were disturbed by Ngugi's harsh criticism of the established social and economic order. In reaction to the novel as well as to his play I Will Marry When I Want, after his release from detention in 1978 Ngugi was not reinstated in his job at Nairobi University, was arrested on trivial charges on several occasions, and received death threats.

Despite its status as a controversial work, the novel was received warmly by most readers and critics. An anonymous early review in Kenya's Weekly Review entitled ‘‘Ngugi's Bombshell’’ said that the Kenyan reader might feel as though Ngugi had been "walking all over your soul'' because of the way he portrayed the results of independence. The reviewer went on to call the work Ngugi's "crowning achievement'' but also noted the work's lack of humor and the people's unconvincing absorption in socialism. Joe Khadi, writing in the Daily Nation, another Kenyan publication, declared that "no writer has yet been able to expose the evils of such a system in as bold and fearless a manner.'' Other early African reviewers noted the novel's political impact, praised its narrative richness, and often criticized its use of Marxist principles.

Many western critics were also complimentary of the novel when it appeared. Christopher Ricks in the Sunday Times of London hailed it as "remarkable’’ and "compelling" for its presentation of political issues and innovative use of language. Novelist John Updike, however, writing in the New Yorker, was not as generous, saying that ‘‘Whatever else political fervor has done for Ngugi, it has not helped his ear for English.''

The novel has enjoyed considerable scholarly attention, and many critics have echoed the sentiments of early reviewers, acknowledging the novel's considerable strengths while pointing out its weaknesses. One persistent criticism has been that the novel's political message is too overt. In his discussion of Ngugi's writings, the scholar G. D. Killam, for example, says also that the novel ‘‘is open to the charge of political attitudinizing in places.’’ He says the call to right the injustices done to peasants and workers with colonial and post-colonial rule is treated at times with a heavy hand. However, Killam finds that the political attitudes and questions examined in the book are tempered by Ngugi's humanism, as throughout the novel his pressing concern is not with the putting forth of a political ideology but to draw attention to the degradation of human beings.

Other critics, however, have seen the novel's didacticism, or effort to teach and put forward a particular viewpoint, as detracting from its power as a work of art. Simon Gikandi faults Ngugi for his ‘‘authorial intrusiveness,’’ saying that it often forces situations and characters to fit into a "predetermined ideological position.’’ He says, for example, that the character of Joseph is not given any psychological development but emerges as a symbol of the ideals of reform that are central to the work. Gikandi suggests that this is a result of the novel being viewed by Ngugi as a means to ‘‘interpret, judge, and pattern the ever-changing African reality’’ and as a useful social tool, much like traditional oracles, whose main purpose is to confront people with meanings and values. Gikandi does not criticize Ngugi's purpose, but finds that the authorial voice in the novel is often jarring. David Cook and Michael Okenimpke...