In this paper, we investigate the spatial structure and dynamical state of the poorly studied old (\(\sim 4\) Gyr) open cluster Trumpler 19 based on reliable cluster members from \(Gaia\)-DR3. The DBSCAN clustering algorithm is used to estimate membership probabilities and select likely cluster members in a normalized 5D parametric space. We identify 859 likely cluster members down to \(G\sim 20\) mag in the field of the cluster. We estimate a cluster radius of \(R_{cl}\sim 18\) arcmin (13.1 pc) based on the radial distribution of the cluster members. We find that the cluster is deficient in faint and low-mass stars (\(G>18.5\) mag) and strong mass segregation has taken place within the cluster. We estimate a core radius of \(R_{c}=3.0\pm 0.2\) arcmin (\(2.2\pm 0.1\) pc) and a tidal radius of \(R_{t}=30.7\pm 9.0\) arcmin (\(22.3\pm 6.5\) pc) for the cluster. We estimate a concentration parameter of \(\log(R_{t}/R_{c})\sim 1.0\), indicating that Trumpler 19 has formed a clear core-halo structure due to dynamical evolution. We investigate the dynamical state of the cluster using 26 blue stragglers (BSs) identified in the cluster. We find that the BSs extend to a radius of \(\sim 10.5\) arcmin (\(3.5R_{c}\)), and 16 of them (\(\sim 62\%\)) are located in the core radius of the cluster. We also find that the BSs are significantly more concentrated than the red giant branch (RGB) and main-sequence (MS) stars, indicating that Trumpler 19 is a dynamically old cluster.