Noninvasive circulating tumor
DNA
(ct
DNA
) can be used to predict breast cancer recurrence and prognosis. In this study, we detected 226 and 114 somatic variants in tumor
DNA
from 70 primary breast cancer (
PBC
) patients (98.59%) and ct
DNA
from 48 patients (67.61%), respectively. Gene frequencies of tumor
DNA
and ct
DNA
significantly correlated (
R
2
= 0.9532,
P
< 0.0001), and tumor‐derived variants were detectable in the blood of 43 patients. ct
DNA
was more often detected in locally advanced/metastatic and nonluminal patients. Multivariate analysis revealed that individual N stage (
P
<
0.001) and hormone receptor (HR) status (
P
=
0.001) could independently predict the detectability of tumor‐derived mutations in blood. The maximal variant allele frequency of ct
DNA
was significantly higher in patients with stage
IV
/M1 (
P
=
0.0136) and stage T3/T4 (
P
=
0.0085) cancers. Finally, clonal variants in tumor
DNA
were more easily traced in ct
DNA
than subclonal variants (84.62% vs 48.75%). In conclusion, ct
DNA
fragments concordant with tumor
DNA
can be consistently detected in the majority of tested
PBC
patients, which may enable noninvasive genomic profiling of
PBC
, particularly for patients with advanced‐stage tumors and positive HR status.