Q. Why don’t we make a bracha before reading Parshat Amalek?

A. A number of reasons are given for not reciting a brocho on reading Pashas Zachor.

a) You don’t make a brocho on something destructive, such as executing a punishment, a death sentence, or performing a Sotah ceremony (Kaf Hachaim 685: 29, Yofe lelev 3: 3, Maharitz Chiyos and Shem Aryeh, quoted in Divrey Shlomo 2, see also Mishne Halochos 7: 81)

b) You do not recite a brocho on a mitzvah that you comply with by just saying that same brocho. Remembering the exodus from Mitzraim, reciting Kidush on Shabbos, or the annulment of chametz are examples mentioned (Magen Haelef 432, Birchas Halevy p. 330)

c) It is a constant, endless mitzvah that always applies, such as visiting the ill, consoling the bereaved or honoring parents (Or Zaruah, Divrey Shlomo ibid.)

d) You don’t recite a brocho on a mitzvah connected to a negative commandment (ibid.)

It is interesting to mention that Har Tzvi (O.H.58) maintains that we do recite a brocho on Pashas Zachor and that is the birchas HaTorah that the oleh LaTorah pronounces before reading begins.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a