Ammonia (NH3) emissions from manure storage in animal feedlots and post-farm treatment facilities, such as composting facilities, are the key contributors to the agricultural NH3 budget. Simultaneous quantification of NH3 emissions from these two sectors at the same site can provide information on NH3 emissions along the manure management chain, which will aid in accurately evaluating best management practices for NH3 mitigation. The NH3 emission rates of a large sheep feedlot with a full capacity of ∼30,000 heads, consisting of occupied pens, unoccupied pens (empty), and a neighboring composting facility for sheep manure in North China, were quantified using the multiple-source determination of an inverse dispersion technique in winter season. This was followed by a year-round measurement to track the NH3 emission patterns (diurnal and seasonal) of these two sectors and further quantify the NH3 emissions. The NH3 flux of the occupied pens was 2.07 and 2.64 times that of the empty pens and the composting facility, respectively. After excluding the NH3 emissions from the empty pens, the NH3 emission rates per head in four seasons changed from 11.01 to 22.43 to 8.58–11.13 g head–1 d–1. The NH3 emissions from the feedlot accounted for 25.26% of the feed N intake (or 33.68% of the excreted N), and the NH3 emissions from the manure composting facility accounted for 2.20% of the initial N in sheep manure. This study is novel in filling the data gap for both the NH3 emissions from sheep feedlots and the representative contributions of different manure management sectors.