The Shulhan Aruch (Orah Haim 51:4) writes that it is forbidden to make any verbal interruptions during the prayer service, from Baruch She’amar – at the beginning of the Pesukeh De’zimra section of the service – until after the Amida. Later Poskim (Halachic authorities) clarify that this includes the Hazan’s repetition of the Amida, as well as the recitation of "Ana" and "Le’David." Throughout this entire segment of the prayer service, Halacha forbids speaking.
Unfortunately, although many people are aware of the prohibition against speaking during Pesukeh De’zimra, there are many people who fail to observe this Halacha. It is all too common to see people speak during the Pesukeh De’zimra section of the service. It must be emphasized that the prohibition against speaking during Pesukeh De’zimra applies regardless of the language in which one speaks. Some people mistakenly think that they are allowed to speak in Hebrew during this section of the service, but this is incorrect. All interruptions are forbidden during Pesukeh De’zimra.
There are, however, a small handful of exceptions to this rule. One such case is when a person is praying Pesukeh De’zimra and realizes that the final time for Shema will soon arrive, and he will not reach Shema by that time. A person in this case may, and should, recite Shema at that point, even though he is in the middle of Pesukeh De’zimra.
It is also permissible during Pesukeh De’zimra to answer the first five "Amen" responses to Kaddish, including the response of "Amen Yeheh Shemeh Rabba" through "Da’amiran Be’alma." Similarly, one may answer "Amen" to any Beracha he hears during Pesukeh De’zimra, and one may respond to "Barechu." One may not, however, answer "Baruch Hu U’baruch Shemo" when hearing a Beracha during Pesukeh De’zimra. Since this customary response is not mentioned anywhere in the Talmud, it does not have the status that allows for interrupting Pesukeh De’zimra.
Summary: It is strictly forbidden to speak during Pesukeh De’zimra. One may, however, recite Shema during Pesukeh De’zimra if he will otherwise miss the final time for the Shema recitation. It is also permissible during Pesukeh De’zimra to answer "Amen" to a Beracha that one hears, to answer the first five "Amen" responses to Kaddish, and to respond to Barechu.
